bluuebunny/crossref_metadata_2025 huggingface dataset:
The Division of Household Labor
Authors: Shelton Beth Anne , John Daphne
Published: July 2002

In this chapter we review research on the division of household labor and its consequences. The review summarizes research focused on issues of measurement, including research on methods of gathering data on housework time and time use in general and discussions of various ways to operationalize the division of household labor. Some attention is paid to historical and theoretical work on housework and women's responsibility for it in particular, followed by a more detailed discussion of current empirical approaches to explaining the division of household labor as well as criticisms of these approaches. Finally, we review research that examines the consequences of the division of household labor, focusing on those studies that examine its impact on labor force participation and wages, marital and family satisfaction, psychological well-being, and perceptions of fairness.
The Trend in Between-Nation Income Inequality
Authors: Firebaugh Glenn
Published: July 2002

About seventy percent of the world's total income inequality is between-nation inequality as opposed to within-nation inequality. Between-nation inequality is the bigger component because average incomes in the richest nations are roughly 30 times greater than average incomes in the poorest nations. This highly uneven distribution of income across nations likely reflects the long-run divergence of national incomes over the course of the Industrial Revolution. Empirical investigations suggest, however, that between-nation income inequality has stabilized in recent decades. Because between-nation inequality has stabilized, the direction of the current trend in total world income inequality depends on the direction of the change in income inequality in the average nation.
Autonomic Tone Variations Before the Onset of Paroxysmal Atrial Fibrillation
Authors: Bettoni Marco , Zimmermann Marc
Published: July 2002

Background

—

Mechanisms favoring the occurrence of paroxysmal atrial fibrillation (PAF) are complex and poorly defined. This study was designed to analyze dynamic changes in autonomic tone preceding the onset of PAF in a large group of patients.

Methods and Results

—

Holter tapes from 77 unselected consecutive patients (63 men and 14 women aged 58±12 years) with PAF were analyzed. A total of 147 episodes of sustained AF (>30 minutes) were recorded and submitted to time-domain and frequency-domain heart rate variability analyses; 6 periods were studied using repeated measures ANOVA: the 24-hour period, the hour preceding PAF, and the 20 minutes before PAF divided into four 5-minute periods. In the time-domain analyses, a linear decrease in mean RR interval from 925±16 to 906±16 ms (
P
<0.0002) was observed before the onset of PAF, together with a significant increase in the standard deviation of NN intervals from 65±4 to 70±4 ms (
P
<0.02). In the frequency-domain analyses, a significant increase in high-frequency (HF, HF-NU) components was observed before PAF (
P
<0.001 and
P
<0.0001, respectively), together with a progressive decrease in low-frequency components (LF, LF-NU) (
P
<0.0001 and
P
<0.004, respectively). The low/high frequency ratio showed a linear increase until 10 minutes before PAF, followed by a sharp decrease immediately before PAF, suggesting a primary increase in adrenergic tone followed by a marked modulation toward vagal predominance. No difference was observed in these heart rate variability changes between patients with “lone” PAF and patients with structural heart disease.

Conclusions

—

The occurrence of PAF greatly depends on variations of the autonomic tone, with a primary increase in adrenergic tone followed by an abrupt shift toward vagal predominance.
Cardiomyocyte Cell Cycle Regulation
Authors: Pasumarthi Kishore B.S. , Field Loren J.
Published: July 2002

Although rapid progress is being made in many areas of molecular cardiology, issues pertaining to the origins of heart-forming cells, the mechanisms responsible for cardiogenic induction, and the pathways that regulate cardiomyocyte proliferation during embryonic and adult life remain unanswered. In the present study, we review approaches and studies that have shed some light on cardiomyocyte cell cycle regulation. For reference, an initial description of cardiomyogenic induction and morphogenesis is provided, which is followed by a summary of published cell cycle analyses during these stages of cardiac ontology. A review of studies examining cardiomyocyte cell cycle analysis and de novo cardiomyogenic induction in the adult heart is then presented. Finally, studies in which cardiomyocyte cell cycle activity was experimentally manipulated in vitro and in vivo are reviewed. It is hoped that this compilation will serve to stimulate thought and experimentation in this intriguing area of cardiomyocyte cell biology.
Does Renal Dysfunction Predict Mortality After Acute Stroke?
Authors: MacWalter Ronald S. , Wong Suzanne Y.S. , Wong Kenneth Y.K. , Stewart Graham , Fraser Callum G. , Fraser Hazel W. , Ersoy Yuksel , Ogston Simon A. , Chen Rouling
Published: July 2002

Background and Purpose

—

The purpose of this study was to investigate renal function as a long-term predictor of mortality in patients hospitalized for acute stroke.

Methods

—

This was a cohort study done in a Scottish tertiary teaching hospital. Participants included 2042 (993 male) unselected consecutive stroke patients (mean age, 73 years) admitted to hospital within 48 hours of stroke between1988 and 1994. Follow-up was up to 7 years. Main outcome measure was all-cause mortality.

Results

—

The total number of deaths at the end of follow-up was 1026. Most subjects (1512) had creatinine <124 μmol/L. The mean calculated creatinine clearance was 54.8 mL/min (SD, 23 mL/min). Renal function indexes were analyzed by quartiles with Cox proportional-hazards model. Stroke survivors had higher calculated creatinine clearance and lower serum creatinine, urea, and ratios of urea to creatinine. Calculated creatinine clearance ≥51.27 mL/min significantly predicted better long-term survival in these stroke patients even after adjustment for confounders (age, neurological score, ischemic heart disease, hypertension, smoking, and diuretic use). Similarly, creatinine ≥119 μmol/L “relative risk (RR), 1.59; 95% confidence interval (CI), 1.32 to 1.92”, urea 6.8 to 8.9 mmol/L (RR, 1.34; 95% CI, 1.09 to 1.65) or ≥9 mmol/L (RR, 1.74; 95% CI, 1.42 to 2.13), and ratio of urea to creatinine ≥0.08573 mmol/μmol (RR, 1.24; 95% CI, 1.03 to 1.50) remained significant predictors of mortality after adjustment for confounders.

Conclusions

—

After acute stroke, patients with reduced admission calculated creatinine clearance, raised serum creatinine and urea concentrations (even within conventional reference intervals), and raised ratio of urea to creatinine had a higher mortality risk. This finding may be used to stratify risk and target interventions, eg, the use of angiotensin-converting enzyme inhibitors.
Increased Anisotropy in Acute Stroke
Authors: Green Hadrian A.L. , Peña Alonso , Price Christopher J. , Warburton Elizabeth A. , Pickard John D. , Carpenter T. Adrian , Gillard Jonathan H.
Published: July 2002

Background and Purpose

—

The increase in fractional anisotropy (FA) in acute stroke has yet to be explained. Using an engineering methodology known as pq diagrams, we sought to explain the increase in FA by describing changes in the total magnitude of the diffusion tensor (L) as well as the isotropic (p) and anisotropic (q) components.

Methods

—

Diffusion tensor imaging was performed in 10 patients with stroke <27 hours old. The diffusion tensor was decomposed into the p and q components and plotted to describe the diffusion trajectories. FA was also calculated and compared.

Results

—

There was significant and consistent reduction in p, q, and L (p: mean, −50.0%; range, −36.6% to −64.5%; q: mean, −50.8%; range, −30.8% to −72.8%; L: mean, −50.3%; range, −37.0% to −65.1%). There were inconsistent changes in FA (mean, −0.5%; range, −44.9% to +45.0%). Five patients had elevated FA due to proportionately higher loss of L than q.

Conclusions

—

Changes in FA only occur when there is a change in the ratio of q/L. Acute elevation of FA occurred in the context of a larger reduction in L than q. The elevation in FA occurs in the context of a reduction in the anisotropic tensor and therefore is a consequence of ratio-metric measurement. This appears to clarify the reported increase in FA in terms of alterations in the shape of the apparent diffusion tensor. pq diagrams appear to offer improved resolution of acute diffusion changes in ischemia.
Trade Blocs, Trade Flows, and International Conflict
Authors: Mansfield Edward D. , Pevehouse Jon C.
Published: July 2002

The relationship between foreign trade and political conflict has been a persistent source of controversy among scholars of international relations. Existing empirical studies of this topic have focused on the effects of trade flows on conflict, but they have largely ignored the institutional context in which trade is conducted. In this article we present some initial quantitative results pertaining to the influence on military disputes of preferential trading arrangements (PTAs), a broad class of commercial institutions that includes free trade areas, common markets, and customs unions. We argue that parties to the same PTA are less prone to disputes than other states and that hostilities between PTA members are less likely to occur as trade flows rise between them. Moreover, we maintain that heightened commerce is more likely to inhibit conflict between states that belong to the same preferential grouping than between states that do not. Our results accord with this argument. Based on an analysis of the period since World War II, we find that trade flows have relatively little effect on the likelihood of disputes between states that do not participate in the same PTA. Within PTAs, however, there is a strong, inverse relationship between commerce and conflict. Parties to such an arrangement are less likely to engage in hostilities than other states, and the likelihood of a military dispute dips markedly as trade increases between them.
Which norms matter? Revisiting the “failure” of internationalism
Authors: Legro Jeffrey W.
Published: July 2002

International relations theorists have in recent years shown an interest in international norms and rules not equaled since the interwar period. This contemporary literature is, of course, quite different—i.e., better—than that of the 1920s and 1930s: it has greater intellectual depth, empirical backing, and explanatory power. The promise of this research, bolstered by the opportunities of the post–cold war era, is that norms encouraging free trade, protecting the environment, enhancing human rights, and controlling the spread and use of heinous weapons may have a substantial impact on the conduct and structure of international relations. But pessimists also exist. Some have taken up the stick E. H. Carr skillfully shook at idealists in an earlier period, arguing that the anarchic power-shaped international arena is not so malleable and that international norms and institutions have relatively little influence. On the one hand, we are pointed to the centrality of international norms; on the other, we are cautioned that norms are inconsequential. How do we make sense of these divergent claims? Which is right?
Reversing the Gun Sights: Transnational Civil Society Targets Land Mines
Authors: Price Richard
Published: July 2002

The rise in the importance of nonstate actors in generating new norms in world politics has been documented by scholars, but the literature has focused predominantly on nonsecurity (“new”) issue areas. Conversely, although recent constructivist work in international relations has examined the security policies of states, typically it is the state that is doing the constructing of interests. I bridge these two literatures by examining the hard case of transnational civil society working through issue networks to teach state interests in security policy. I analyze the campaign by transnational civil society to generate an international norm prohibiting antipersonnel land mines and trace the effects of several techniques through which states can be said to be socialized. Through generating issues, networking, “grafting,” and using a transnational Socratic method to reverse burdens of proof, the campaign has stimulated systemic normative change through two processes: norm adoption through the conversion of persuaded moral entrepreneurs and emulation resulting from social pressures of identity.
Bargaining, Enforcement, and International Cooperation
Authors: Fearon James D.
Published: July 2002

Neoliberals and their neorealist critics have debated the relative importance of two main obstacles to international cooperation—problems of cheating and enforcement and problems of relative gains. By contrast, I argue that problems of international cooperation have a common strategic structure in which a third, distinct obstacle plays a crucial role. Almost regardless of the issue area, states must first resolve the bargaining problem of agreeing on terms before they can implement and begin to enforce an agreement. Furthermore, the bargaining and enforcement problems interact. Using a game model, I show that if states must bargain to determine the deal to be enforced, the “shadow of the future” cuts two ways. A high expectation of continued interactions may make enforcing the agreement easier, but it can also give states an incentive to bargain harder, delaying agreement in hopes of getting a better deal. Empirical evidence from trade and arms control negotiations suggests that this mechanism may help to explain the costly standoffs that are often observed in international politics and are problematic for received neoliberal theories.
A Painter's Eye Movements: A Study of Eye and Hand Movement during Portrait Drawing
Authors: Miall R.C. , Tchalenko John
Published: July 2002

The mental processes that al-low an artist to transform visual images-e.g. those of his model-into a picture on the canvas are not easily studied. The authors re-port work measuring the eye and hand movements of a single artist, chosen for his detailed and realis-tic portraits produced from life. His eye fixations when painting or drawing were of twice the duration of those when he was not painting and also quite different from those of novice artists. His eye-hand co-ordination pattern also showed dif-ferences from that of novices, be-ing more temporally consistent. This preliminary work suggests that detailed and quantitative analy-sis of a working artist is feasible and will illuminate the process of artistic creation.
On the Relation between Syntactic Phrases and Phonological Phrases
Authors: Truckenbrodt Hubert
Published: July 2002

This article argues that the relation between syntactic XPs and phonological phrases is subject to a constraint, WRAP-XP, that demands that each XP be contained in a phonological phrase. WRAP-XP is argued to interact with the constraints on edge alignment proposed by Selkirk (1986, 1995), with a constraint against recursive structure, and with a constraint aligning an edge of a focus with a phonological phrase. WRAP-XP is intended to replace, and improve on, an earlier proposal by Hale and Selkirk (1987) to the effect that lexical government plays a role in the syntax-prosody mapping. The languages discussed in more detail are Tohono O'odham, Kimatuumbi, and Chicheŵa.
Bare and Not-So-Bare Nouns and the Structure of NP
Authors: Cheng Lisa Lai-Shen , Sybesma Rint
Published: July 2002

This article examines the distribution and interpretational variability of bare nouns and [classifier+noun] phrases in Cantonese and Mandarin. We argue that bare nouns are never bare in structure and that [classifier+noun] phrases may have more structure than just Classifier Phrase. We show that the lack of articles and number morphology in Cantonese/Mandarin leads to many interesting differences between Chinese-type languages and English-/Italian-type languages.
Output Units of Motor Behavior: An Experimental and Modeling Study
Authors: Loeb E. P. , Giszter S. F. , Bizzi P. Saltiel and E. , Mussa-Ivaldi F. A.
Published: July 2002

Cognitive approaches to motor control typically concern sequences of discrete actions without taking into account the stunning complexity of the geometry and dynamics of the muscles. This begs the question: Does the brain convert the intricate, continuous-time dynamics of the muscles into simpler discrete units of actions, and if so, how? One way for the brain to form discrete units of behavior from muscles is through the synergistic co-activation of muscles. While this possibility has long been known, the composition of potential muscle synergies has remained elusive. In this paper, we have focused on a method that allowed us to examine and compare the limb stabilization properties of all possible muscle combinations. We found that a small set (as few as 23 out of 65,536) of all possible combinations of 16 limb muscles are robust with respect to activation noise: these muscle combinations could stabilize the limb at predictable, restricted portions of the workspace in spite of broad variations in the force output of their component muscles. The locations at which the robust synergies stabilize the limb are not uniformly distributed throughout the leg's workspace, but rather, they cluster at four workspace areas. The simulated robust synergies are similar to the actual synergies we have previously found to be generated by activation of the spinal cord. Thus, we have developed a new analytical method that enabled us to select a few muscle synergies with interesting properties out of the set of possible muscle combinations. Beyond this, the identification of robustness as a common property of the synergies in simple motor behaviors will open the way to the study of dynamic stability, which is an important and distinct property of the vertebrate motor-control system.
I. The Neurocognitive Profile of Williams Syndrome: A Complex Pattern of Strengths and Weaknesses
Authors: Bellugi Ursula , Lichtenberger Liz , Jones Wendy , Lai Zona , St. George Marie
Published: July 2002

The rare, genetically based disorder, Williams syndrome (WMS), produces a constellation of distinctive cognitive, neuroanatomical, and electrophysiological features which we explore through the series of studies reported here. In this paper, we focus primarily on the cognitive characteristics of WMS and begin to forge links among these characteristics, the brain, and the genetic basis of the disorder. The distinctive cognitive profile of individuals with WMS includes relative strengths in language and facial processing and profound impairment in spatial cognition. The cognitive profile of abilities, including what is ‘typical’ for individuals with WMS is discussed, but we also highlight areas of variability across the group of individuals with WMS that we have studied. Although the overall cognitive abilities (IQs) of individuals with WMS are typically in the mild-to-moderate range of mental retardation, the peaks and valleys within different cognitive domains make this syndrome especially intriguing to study across levels. Understanding the brain basis (and ultimately the genetic basis) for higher cognitive functioning is the goal we have begun to undertake with this line of interdisciplinary research.
The Psychophysiology of Real-Time Financial Risk Processing
Authors: Lo Andrew W. , Repin Dmitry V.
Published: July 2002

A longstanding controversy in economics and finance is whether financial markets are governed by rational forces or by emotional responses. We study the importance of emotion in the decision-making process of professional securities traders by measuring their physiological characteristics (e.g., skin conductance, blood volume pulse, etc.) during live trading sessions while simultaneously capturing real-time prices from which market events can be detected. In a sample of 10 traders, we find statistically significant differences in mean electrodermal responses during transient market events relative to no-event control periods, and statistically significant mean changes in cardiovascular variables during periods of heightened market volatility relative to normal-volatility control periods. We also observe significant differences in these physiological responses across the 10 traders that may be systematically related to the traders' levels of experience.
Patterns of Bimanual Interference Reveal Movement Encoding within a Radial Egocentric Reference Frame
Authors: Swinnen Stephan P. , Dounskaia Natalia , Duysens Jacques
Published: July 2002

Constraints on interlimb coordination have been studied intensively in past years with a primary focus on temporal features. The present study addressed spatial constraints or the degree of directional interference as a function of different line combinations between the upper limbs as well as the modulation of this interference as a result of different board orientations within the performer's workspace. This paradigm was used to address a prominent theme in motor neuroscience, namely whether (bimanual) movements are encoded within an allocentric reference frame (pattern of interference invariant with respect to extrinsic space) or within an egocentric reference frame (pattern of interference invariant relative to the center of the performer's action space, i.e., intrinsic). The observed patterns of interference revealed that movements are primarily encoded within a radial egocentric reference frame in which the performer is the center of action space. The present psychophysical findings converge with primate single-cell recording studies in which the direction has been identified as a primary movement parameter that is encoded in various brain regions, thereby constituting a principal determinant of bilateral interference.
Neuroanatomical Correlates of Human Reasoning
Authors: Goel Vinod , Gold Brian , Kapur Shitij , Houle Sylvain
Published: July 2002

One of the important questions cognitive theories of reasoning must address is whether logical reasoning is inherently sentential or spatial. A sentential model would exploit nonspatial (linguistic) properties of representations whereas a spatial model would exploit spatial properties of representations. In general terms, the linguistic hypothesis predicts that the language processing regions underwrite human reasoning processes, and the spatial hypothesis suggests that the neural structures for perception and motor control contribute the basic representational building blocks used for high-level logical and linguistic reasoning. We carried out a [15O] H2O PET imaging study to address this issue.

Twelve normal volunteers performed three types of deductive reasoning tasks (categorical syllogisms, three-term spatial relational items, and three-term nonspatial relational items) while their regional cerebral blood flow pattern was recorded using [15O] H2O PET imaging. In the control condition subjects

semantically comprehended sets of three sentences. In the deductive reasoning conditions subjects determined whether the third sentence was entailed by the first two sentences.

The areas of activation in each reasoning condition were confined to the left hemisphere and were similar to each other and to activation reported in previous studies. They included the left inferior frontal gyrus (Brodmann areas 45, 47), a portion of the left middle frontal gyrus (Brodmann area 46), the left middle temporal gyrus (Brodmann areas 21, 22), a region of the left lateral inferior temporal gyrus and superior temporal gyrus (Brodmann areas 22, 37), and a portion of the left cingulate gyrus (Brodmann areas 32, 24). There was no significant right- hemisphere or parietal activation. These results are consistent with previous neuroimaging studies and raise questions about the level of involvement of classic spatial regions in reasoning about linguistically presented spatial relations.
Reactivation of a Dormant Representation of an Auditory Stimulus Feature
Authors: Ritter Walter , Gomes Hilary , Cowan Nelson , Sussman Elyse , Vaughan Herbert G.
Published: July 2002

Research with the mismatch negativity component of event-related potentials has uncovered a system that detects change in the acoustic environment on an automatic basis. The system is considered to compare incoming stimuli to representations of the past and to emit an MMN if change is detected. Previous investigations have shown that the relevant memory of the past can become dormant and then be reactivated by a reminder stimulus. It is unclear, however, whether what is reactivated is an holistic representation of stimuli or separate representations of features of stimuli. The present study provides data that supports the latter possibility but leaves open the former one.
Graded Functional Activation in the Visuospatial System with the Amount of Task Demand
Authors: Carpenter P. A. , Just M. A. , Keller T. A. , Eddy W. , Thulborn K.
Published: July 2002

Two studies examined how the amount and type of computational demand are related to fMRI-measured activation in three bilateral cortical regions involved in the Shepard-Metzler (1971) mental-rotation paradigm. The amount of demand for the computation of visuospatial coordinates was manipulated by presenting mental rotation problems with increasing angular disparity (0, 40, 80, or 120°). Activation in both the left and right intraparietal sulcal regions increased linearly with angular disparity in two separate studies. Activation also occurred in the fusiform gyrus and inferior temporal regions, regions that are primarily associated with the processes of object and object-part identification. By contrast, the demand for object recognition and rotation processes was relatively low, and the demand for executing saccades was high in a control condition that required making a systematic visual scan of two grids. The grid-scanning condition resulted in relatively less activation in the parietal and inferior temporal regions but considerable activation in frontal areas that are associated with planning and executing saccades, including the precentral gyrus and sulcus into the posterior middle frontal region. These data suggest that the amount of activation in the various cortical regions that support visuospatial processing is related to the amount, as well as to the type, of computational demand.
Aging and Recognition Memory: Changes in Regional Cerebral Blood Flow Associated with Components of Reaction Time Distributions
Authors: Madden David J. , Gottlob Lawrence R. , Denny Laura L. , Turkington Timothy G. , Provenzale James M. , Hawk Thomas C. , Coleman R. Edward
Published: July 2002

We used H2 15O positron emission tomography (PET) to measure age-related changes in regional cerebral blood flow (rCBF) during a verbal recognition memory task. Twelve young adults (20 to 29 years) and 12 older adults (62 to 79 years) participated. Separate PET scans were conducted during Encoding, Baseline, and Retrieval conditions. Each of the conditions involved viewing a series of 64 words and making a two-choice response manually. The complete reaction time (RT) distributions in each task condition were characterized in terms of an ex-Gaussian model (convolution of exponential and Gaussian functions). Parameter estimates were obtained for the mean of the exponential component (τ), representing a task-specific decision process and the mean of the Gaussian component (μ), representing residual sensory coding and response processes. Independently of age group, both μ and τ were higher in the Encoding and Retrieval conditions than in the Baseline condition, and τ was higher during Retrieval than during Encoding. Age-related slowing in task performance was evident primarily in μ. For young adults, rCBF activation in the right prefrontal cortex, in the Retrieval condition, was correlated positively with μ but not with τ. For older adults, rCBF changes (both increases and decreases) in several cortical regions were correlated with both μ and τ. The data suggest that the attentional demands of this task are relatively greater for older adults and consequently lead to the recruitment of additional neural systems during task performance.
Target Selection for Pursuit and Saccadic Eye Movements in Humans
Authors: Krauzlis R. J. , Zivotofsky A. Z. , Miles F. A.
Published: July 2002

Eye movements were recorded from three subjects as they initiated tracking of a small circle (“target”) moving leftward or rightward, above or below the horizontal meridian, either alone or in the presence of a small square (“distractor”) moving leftward or rightward on the other side of the horizontal meridian. At the start of each trial, subjects were provided with either a “form” cue (always centrally positioned and having the circular shape and color of the upcoming moving target) or a “location” cue (a small white square positioned where the upcoming target would appear). The latency of pursuit increased in the presence of an oppositely moving distractor when subjects were provided the form cues but not when they were provided the location cues. The latency of saccades showed similar, but smaller, increases when subjects were given the form cues. On many trials with the form cues, pursuit started in the direction of the distractor and then reversed to follow the target. On these trials, the initial saccade often, but not always, also followed the distractor. These results indicate that the mechanisms of target selection for pursuit and saccades are tightly coordinated but not strictly yoked. The shared effects of the distractor on the latencies of pursuit and saccades probably reflect the common role of visual attention in filtering the inputs that guide these two types of eye movements. The differences in the details of the effects on pursuit and saccades suggest that the neural mechanisms that trigger these two movements can be independently regulated.
On the Computational Complexity of Binary and Analog Symmetric Hopfield Nets
Authors: Šíma Jiří , Orponen Pekka , Antti-Poika Teemu
Published: July 2002

We investigate the computational properties of finite binary- and analog-state discrete-time symmetric Hopfield nets. For binary networks, we obtain a simulation of convergent asymmetric networks by symmetric networks with only a linear increase in network size and computation time. Then we analyze the convergence time of Hopfield nets in terms of the length of their bit representations. Here we construct an analog symmetric network whose convergence time exceeds the convergence time of any binary Hopfield net with the same representation length. Further, we prove that the MIN ENERGY problem for analog Hopfield nets is NP-hard and provide a polynomial time approximation algorithm for this problem in the case of binary nets. Finally, we show that symmetric analog nets with an external clock are computationally Turing universal.
Learning Chaotic Attractors by Neural Networks
Authors: Bakker Rembrandt , Schouten Jaap C. , Giles C. Lee , Takens Floris , Bleek Cor M. van den
Published: July 2002

An algorithm is introduced that trains a neural network to identify chaotic dynamics from a single measured time series. During training, the algorithm learns to short-term predict the time series. At the same time a criterion, developed by Diks, van Zwet, Takens, and de Goede (1996) is monitored that tests the hypothesis that the reconstructed attractors of model-generated and measured data are the same. Training is stopped when the prediction error is low and the model passes this test. Two other features of the algorithm are (1) the way the state of the system, consisting of delays from the time series, has its dimension reduced by weighted principal component analysis data reduction, and (2) the user-adjustable prediction horizon obtained by “error propagation”—partially propagating prediction errors to the next time step.

The algorithm is first applied to data from an experimental-driven chaotic pendulum, of which two of the three state variables are known. This is a comprehensive example that shows how well the Diks test can distinguish between slightly different attractors. Second, the algorithm is applied to the same problem, but now one of the two known state variables is ignored. Finally, we present a model for the laser data from the Santa Fe time-series competition (set A). It is the first model for these data that is not only useful for short-term predictions but also generates time series with similar chaotic characteristics as the measured data.
Observable Operator Models for Discrete Stochastic Time Series
Authors: Jaeger Herbert
Published: July 2002

A widely used class of models for stochastic systems is hidden Markov models. Systems that can be modeled by hidden Markov models are a proper subclass of linearly dependent processes, a class of stochastic systems known from mathematical investigations carried out over the past four decades. This article provides a novel, simple characterization of linearly dependent processes, called observable operator models. The mathematical properties of observable operator models lead to a constructive learning algorithm for the identification of linearly dependent processes. The core of the algorithm has a time complexity of O (N + nm3), where N is the size of training data, n is the number of distinguishable outcomes of observations, and m is model state-space dimension.
Adaptive Method of Realizing Natural Gradient Learning for Multilayer Perceptrons
Authors: Amari Shun-ichi , Park Hyeyoung , Fukumizu Kenji
Published: July 2002

The natural gradient learning method is known to have ideal performances for on-line training of multilayer perceptrons. It avoids plateaus, which give rise to slow convergence of the backpropagation method. It is Fisher efficient, whereas the conventional method is not. However, for implementing the method, it is necessary to calculate the Fisher information matrix and its inverse, which is practically very difficult. This article proposes an adaptive method of directly obtaining the inverse of the Fisher information matrix. It generalizes the adaptive Gauss-Newton algorithms and provides a solid theoretical justification of them. Simulations show that the proposed adaptive method works very well for realizing natural gradient learning.
Reinforcement Learning in Continuous Time and Space
Authors: Doya Kenji
Published: July 2002

This article presents a reinforcement learning framework for continuous-time dynamical systems without a priori discretization of time, state, and action. Basedonthe Hamilton-Jacobi-Bellman (HJB) equation for infinite-horizon, discounted reward problems, we derive algorithms for estimating value functions and improving policies with the use of function approximators. The process of value function estimation is formulated as the minimization of a continuous-time form of the temporal difference (TD) error. Update methods based on backward Euler approximation and exponential eligibility traces are derived, and their correspondences with the conventional residual gradient, TD (0), and TD (λ) algorithms are shown. For policy improvement, two methods—a continuous actor-critic method and a value-gradient-based greedy policy—are formulated. As a special case of the latter, a nonlinear feedback control law using the value gradient and the model of the input gain is derived. The advantage updating, a model-free algorithm derived previously, is also formulated in the HJB-based framework.

The performance of the proposed algorithms is first tested in a nonlinear control task of swinging a pendulum up with limited torque. It is shown in the simulations that (1) the task is accomplished by the continuous actor-critic method in a number of trials several times fewer than by the conventional discrete actor-critic method; (2) among the continuous policy update methods, the value-gradient-based policy with a known or learned dynamic model performs several times better than the actor-critic method; and (3) a value function update using exponential eligibility traces is more efficient and stable than that based on Euler approximation. The algorithms are then tested in a higher-dimensional task: cart-pole swing-up. This task is accomplished in several hundred trials using the value-gradient-based policy with a learned dynamic model.
A Complex Cell-Like Receptive Field Obtained by Information Maximization
Authors: Okajima Kenji , Imaoka Hitoshi
Published: July 2002

The energy model (Pollen & Ronner, 1983; Adelson & Bergen, 1985) for a complex cell in the visual cortex is investigated theoretically. The energy model describes the output of a complex cell as the squared sum of outputs of two linear operators. An information-maximization problem to determine the two linear operators is investigated assuming the low signal-to-noise ratio limit and a localization term in the objective function. As a result, two linear operators characterized by a quadrature pair of Gabor functions are obtained as solutions. The result agrees with the energy model, which well describes the shift-invariant and orientation-selective responses of actual complex cells, and thus suggests that complex cells are optimally designed from an information-theoretic viewpoint.
Improvements to Platt's SMO Algorithm for SVM Classifier Design
Authors: Keerthi S. S. , Shevade S. K. , Bhattacharyya C. , Murthy K. R. K.
Published: July 2002

This article points out an important source of inefficiency in Platt's sequential minimal optimization (SMO) algorithm that is caused by the use of a single threshold value. Using clues from the KKT conditions for the dual problem, two threshold parameters are employed to derive modifications of SMO. These modified algorithms perform significantly faster than the original SMO on all benchmark data sets tried.
A Unified Approach to the Study of Temporal, Correlational, and Rate Coding
Authors: Panzeri Stefano , Schultz Simon R.
Published: July 2002

We demonstrate that the information contained in the spike occurrence times of a population of neurons can be broken up into a series of terms, each reflecting something about potential coding mechanisms. This is possible in the coding regime in which few spikes are emitted in the relevant time window. This approach allows us to study the additional information contributed by spike timing beyond that present in the spike counts and to examine the contributions to the whole information of different statistical properties of spike trains, such as firing rates and correlation functions. It thus forms the basis for a new quantitative procedure for analyzing simultaneous multiple neuron recordings and provides theoretical constraints on neural coding strategies. We find a transition between two coding regimes, depending on the size of the relevant observation timescale. For time windows shorter than the timescale of the stimulus-induced response fluctuations, there exists a spike count coding phase, in which the purely temporal information is of third order in time. For time windows much longer than the characteristic timescale, there can be additional timing information of first order, leading to a temporal coding phase in which timing information may affect the instantaneous information rate.

In this new framework, we study the relative contributions of the dynamic firing rate and correlation variables to the full temporal information, the interaction of signal and noise correlations in temporal coding, synergy between spikes and between cells, and the effect of refractoriness. We illustrate the utility of the technique by analyzing a few cells from the rat barrel cortex.
Manifold Stochastic Dynamics for Bayesian Learning
Authors: Zlochin Mark , Baram Yoram
Published: July 2002

We propose a new Markov Chain Monte Carlo algorithm, which is a generalization of the stochastic dynamics method. The algorithm performs exploration of the state-space using its intrinsic geometric structure, which facilitates efficient sampling of complex distributions. Applied to Bayesian learning in neural networks, our algorithm was found to produce results comparable to the best state-of-the-art method while consuming considerably less time.
An Equivalence Between Sparse Approximation and Support Vector Machines
Authors: Girosi Federico
Published: July 2002

This article shows a relationship between two different approximation techniques: the support vector machines (SVM), proposed by V. Vapnik (1995) and a sparse approximation scheme that resembles the basis pursuit denoising algorithm (Chen, 1995; Chen, Donoho, & Saunders, 1995). SVM is a technique that can be derived from the structural risk minimization principle (Vapnik, 1982) and can be used to estimate the parameters of several different approximation schemes, including radial basis functions, algebraic and trigonometric polynomials, B-splines, and some forms of multilayer perceptrons. Basis pursuit denoising is a sparse approximation technique in which a function is reconstructed by using a small number of basis functions chosen from a large set (the dictionary). We show that if the data are noiseless, the modified version of basis pursuit denoising proposed in this article is equivalent to SVM in the following sense: if applied to the same data set, the two techniques give the same solution, which is obtained by solving the same quadratic programming problem. In the appendix, we present a derivation of the SVM technique in the framework of regularization theory, rather than statistical learning theory, establishing a connection between SVM, sparse approximation, and regularization theory.
Transform-Invariant Recognition by Association in a Recurrent Network
Authors: Parga Néstor , Rolls Edmund
Published: July 2002

Objects can be reconized independently of the view they present, of their position on the retina, or their scale. It has been suggested that one basic mechanism that makes this possible is a memory effect, or a trace, that allows associations to be made between consecutive views of one object. In this work, we explore the possibility that this memory trace is provided by the sustained activity of neurons in layers of the visual pathway produced by an extensive recurrent connectivity. We describe a model that contains this high recurrent connectivity and synaptic efficacies built with contributions from associations between pairs of views that is simple enough to be treated analytically. The main result is that there is a change of behavior as the strength of the association between views of the same object, relative to the association within each view of an object, increases. When its value is small, sustained activity in the network is produced by the views themselves. As it increases above a threshold value, the network always reaches a particular state (which represents the object) independent of the particular view that was seen as a stimulus. In this regime, the network can still store an extensive number of objects, each defined by a finite (although it can be large) number of views.
Comparison of Multiobjective Evolutionary Algorithms: Empirical Results
Authors: Zitzler Eckart , Deb Kalyanmoy , Thiele Lothar
Published: July 2002

In this paper, we provide a systematic comparison of various evolutionary approaches to multiobjective optimization using six carefully chosen test functions. Each test function involves a particular feature that is known to cause difficulty in the evolutionary optimization process, mainly in converging to the Pareto-optimal front (e.g., multimodality and deception). By investigating these different problem features separately, it is possible to predict the kind of problems to which a certain technique is or is not well suited. However, in contrast to what was suspected beforehand, the experimental results indicate a hierarchy of the algorithms under consideration. Furthermore, the emerging effects are evidence that the suggested test functions provide sufficient complexity to compare multiobjective optimizers. Finally, elitism is shown to be an important factor for improving evolutionary multiobjective search.
Convergence in Evolutionary Programs with Self-Adaptation
Authors: Greenwood Garrison W. , Zhu Qiji J.
Published: July 2002

Evolutionary programs are capable of finding good solutions to difficult optimization problems. Previous analysis of their convergence properties has normally assumed the strategy parameters are kept constant, although in practice these parameters are dynamically altered. In this paper, we propose a modified version of the 1/5-success rule for self-adaptation in evolution strategies (ES). Formal proofs of the long-term behavior produced by our self-adaptation method are included. Both elitist and non-elitist ES variants are analyzed. Preliminary tests indicate an ES with our modified self-adaptation method compares favorably to both a non-adapted ES and a 1/5-success rule adapted ES.
LEGISLATION AND LEGITIMATION IN OMAN: THE BASIC LAW
Authors: Siegfried Nikolaus
Published: July 2002

When Sultan Qabus issued Decree 101 on November 6, 1996, Oman was the last Arab country to implement a constitutional document. However, the political impact of this document is controversial: Whereas some consider the Basic Law a step towards democratization, others see merely a continuation of traditional policies. In this article I investigate the innovative potential of the Basic Law. Against the background of Omani and regional history and European and Islamic constitutional thought, I review the Decree with regard to authority and legitimation. I suggest that the law is mainly symbolic in character. It exploits tribal and Islamic concepts to create a historically unfounded notion of a homogeneous state. The civil liberties it grants do not extend to the public sphere. I conclude that Oman's Basic Law does nothing more than to freeze the status quo, according to which the Sultan remains the only recognized authority in the state.
DAS UNERLEDIGTE PROBLEM DES BUCHES HABAKKUK
Authors:   Herrmann
Published: July 2002

Die zeitgeschichtliche Einbettung der Prophetie Habakkuks gegen Ende des 7. Jahrhunderts v. Chr. scheint zu einer communis opinio geworden zu sein, weniger das literarkritische Urteil über die drei Kapitel. Jedoch widerrät der ideelle Gesamtduktus des kleinen Schriftwerkes einer Aufgliederung in differente literarische Schichten. Die unverkennbar hervortretende Glaubenshaltung des Autors und der Versuch, sein und seiner Mitlebenden Schicksal von daher zu bewältigen, verweist überdies das Buch Habakkuk in ein fortgeschrittenes Stadium frühjüdischer Geschichte.
FEMALES OF A STREAM GOBY CHOOSE MATES THAT COURT IN FAST WATER CURRENTS
Authors: Takahashi Daisuke , Kohda Masanori
Published: July 2002

Males of the stream goby Rhinogobius sp. DA with exclusive paternal care court females in fast water currents. Female choice of this goby was observed in the field. A fast current itself does not seem to be advantageous to females for mating. Neither large male size nor long male dorsal fin, both being sexually dimorphic traits, was related to female selectivity. Females favored males that courted on points at which the water current was relatively fast. Water velocity at male courtship points was positively correlated with a condition factor for males, indicating that males of poor physical condition do not court in fast water currents. Hence, this mate choice pattern enables females to mate with males of good physical condition. Male condition factor itself, however, was not related to selectivity by females. Circumstantial evidence suggest that this female choice pattern will result in mating with males having sufficient energy reserves, i.e. high parental quality.