bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing Risks, Costs, and Benefits of Laparoscopic Hernia Repair
Authors: Memon Muhammed Ashraf , Fitzgibbons Robert J.
Published: July 2002

Laparoscopic inguinal herniorrhaphy (LIHR) was introduced with the following potential advantages: less postoperative discomfort and pain, reduced recovery time that allows earlier return to full activity, easier repair of a recurrent hernia, the ability to treat bilateral hernias concurrently, the performance of a simultaneous diagnostic laparoscopy, ligation of the hernia sac at the highest possible site, improved cosmesis, and decreased incidence of recurrence. Potential disadvantages include complications, such as bowel, bladder, and vascular injuries; potential adhesive complications at sites where the peritoneum has been breached or prosthetic material has been placed; the apparent need, at least at the present, for a general anesthetic; and the increased cost because of expensive equipment needs. Most surgeons agree that LIHR has a role in the management of patients with a recurrent hernia after a conventional inguinal herniorrhaphy (CIHR), bilateral inguinal hernia, or a need for laparoscopy for another procedure, such as laparoscopic cholecystectomy. The routine use of LIHR for the unilateral, uncomplicated hernia is a more contentious issue.
Molecular Genetics and Pathogenesis of Autosomal Dominant Polycystic Kidney Disease
Authors: Arnaout M. Amin
Published: July 2002

▪ Abstract  Autosomal dominant polycystic kidney disease (ADPKD) is a common and systemic disease characterized by formation of focal cysts. Of the three potential causes of cysts, downstream obstruction, compositional changes in extracellular matrix, and proliferation of partially dedifferentiated cells, evidence strongly supports the latter as the primary abnormality. In the vast majority of cases, the disease is caused by mutations in PKD1 or PKD2, and appears to be recessive at the cellular level. Somatic second hits in the normal allele of cells containing the germ line mutation initiate or accelerate formation of cysts. The intrinsically high frequency of somatic second hits in epithelia appears to be sufficient to explain the frequent occurrence of somatic second hits in the disease-causing genes. PKD1 and PKD2 encode a putative adhesive/ion channel regulatory protein and an ion channel, respectively. The two proteins interact directly in vitro. Their cellular and subcellular localization suggest that they may also function independently in a common signaling pathway that may involve the membrane skeleton and that links cell-cell and cell-matrix adhesion to the development of cell polarity.
HOW DO ANIMAL DNA VIRUSES GET TO THE NUCLEUS?
Authors: Kasamatsu H. , Nakanishi A.
Published: July 2002

▪ Abstract  Genome and pre-genome replication in all animal DNA viruses except poxviruses occurs in the cell nucleus ( Table 1 ). In order to reproduce, an infecting virion enters the cell and traverses through the cytoplasm toward the nucleus. Using the cell's own nuclear import machinery, the viral genome then enters the nucleus through the nuclear pore complex. Targeting of the infecting virion or viral genome to the multiplication site is therefore an essential process in productive viral infection as well as in latent infection and transformation. Yet little is known about how infecting genomes of animal DNA viruses reach the nucleus in order to reproduce. Moreover, this nuclear locus for viral multiplication is remarkable in that the sizes and composition of the infectious particles vary enormously. In this article, we discuss virion structure, life cycle to reproduce infectious particles, viral protein's nuclear import signal, and viral genome nuclear targeting.
Polyphosphate and Phosphate Pump
Authors: Kulaev I. , Kulakovskaya T.
Published: July 2002

▪ Abstract  In microbial cells, inorganic polyphosphate (polyP) plays a significant role in increasing cell resistance to unfavorable environmental conditions and in regulating different biochemical processes. polyP is a polyfunctional compound. The most important of its functions are the following: phosphate and energy reservation, cation sequestration and storage, membrane channel formation, participation in phosphate transport, involvement in cell envelope formation and function, gene activity control, regulation of enzyme activities, and a vital role in stress response and stationary-phase adaptation. The functions of polyP have changed greatly during the evolution of living organisms. In prokaryotes, the most important functions are as an energy source and a phosphate reserve. In eukaryotic microorganisms, the regulatory functions predominate. Therefore, a great difference is observed between prokaryotes and eukaryotes in their polyP-metabolizing enzymes. Some key prokaryotic enzymes are not present in eukaryotes, and conversely, eukaryotes have developed new polyP-metabolizing enzymes that are not present in prokaryotes. The synthesis and degradation of polyP in each specialized organelle and compartment of eukaryotic cells are mediated by different sets of enzymes. This is consistent with the endosymbiotic hypothesis of eukaryotic cell origin.
ETIOLOGY AND PATHOGENESIS OF PARKINSON'S DISEASE
Authors: Olanow C. W. , Tatton W. G.
Published: July 2002

▪ Abstract  Parkinson's disease (PD) is an age-related neurodegenerative disorder that affects approximately 1 million persons in the United States. It is characterized by resting tremor, rigidity, bradykinesia or slowness, gait disturbance, and postural instability. Pathological features include degeneration of dopaminergic neurons in the substantia nigra pars compacta coupled with intracytoplasmic inclusions known as Lewy bodies. Neurodegeneration and Lewy bodies can also be found in the locus ceruleus, nucleus basalis, hypothalamus, cerebral cortex, cranial nerve motor nuclei, and central and peripheral components of the autonomic nervous system. Current treatment consists of a dopamine replacement strategy using primarily the dopamine precursor levodopa. While levodopa provides benefit to virtually all PD patients, after 5–10 years of treatment the majority of patients develop adverse events in the form of dyskinesia (involuntary movements) and fluctuations in motor response. Further, disease progression is associated with the development of dementia, autonomic dysfunction, and postural instability, which do not respond to levodopa therapy. Accordingly, research efforts have been directed toward understanding the etiology and pathogenesis of PD in the hope of developing a more effective therapy that will slow or halt the natural progression of PD. This paper reviews recent advances.
NEUTRINOPROPAGATION INDENSEASTROPHYSICALSYSTEMS
Authors: Prakash Madappa , Lattimer James M. , Sawyer Raymond F. , Volkas Raymond R.
Published: July 2002

▪ Abstract  Even the elusive neutrinos are trapped in matter, albeit transiently, in several astrophysical circumstances. Their interactions with the ambient matter not only reveal the properties of such exotic matter, but also shed light on the fundamental properties of the neutrinos. The physical sites of interest include the early universe, supernovae, and newly born neutron stars. Detection of neutrinos from these vastly different eras using the new generation of neutrino detectors holds great promise for enhancing our understanding of neutrino-matter interactions and astrophysical phenomena.
NEURONAL INJURY ASSOCIATED WITH HIV-1: Approaches to Treatment
Authors: Lipton Stuart A.
Published: July 2002

▪ Abstract  Mounting evidence suggests that cognitive dysfunction developing as a result of HIV-1 infection is mediated at least in part by generation of excitotoxins and free radicals in the brain. This syndrome is currently designated HIV-1-associated cognitive/motor complex, was originally termed the AIDS Dementia Complex, and for simplicity, is called AIDS dementia in this review. Recently, brains of patients with AIDS have been shown to manifest neuronal injury and apoptotic-like cell death. How can HIV-1 result in neuronal damage if neurons themselves are only rarely, if ever, infected by the virus? Experiments from several different laboratories have lent support to the existence of HIV- and immune-related toxins in a variety of in vitro and in vivo paradigms. In one recently defined pathway to neuronal injury, HIV-infected macrophages and microglia, or immune-activated macrophages and astrocytes (activated by the shed HIV-1 envelope protein, gp120, or other viral proteins and cytokines), appear to secrete excitants and neurotoxins. These substances may include arachidonic acid, platelet-activating factor, free radicals (NO•and O2•−), glutamate, quinolinate, cysteine, amines, and as yet unidentified factors emanating from stimulated macrophages and reactive astrocytes. A final common pathway for neuronal susceptibility is operative, similar to that observed in stroke and several neurodegenerative diseases. This mechanism involves excessive activation of N-methyl-d-aspartate (NMDA) receptor–operated channels, with resultant excessive influx of Ca2+and the generation of free radicals, leading to neuronal damage. With the very recent development of clinically tolerated NMDA antagonists, there is hope for future pharmacological intervention.
EXCITATORY AMINO ACID TRANSPORTERS: A Family in Flux
Authors: Seal R. P. , Amara S. G.
Published: July 2002

▪ Abstract  As the most predominant excitatory neurotransmitter, glutamate has the potential to influence the function of most neuronal circuits in the central nervous system. To limit receptor activation during signaling and prevent the overstimulation of glutamate receptors that can trigger excitotoxic mechanisms and cell death, extracellular concentrations of excitatory amino acids are tightly controlled by transport systems on both neurons and glial cells. l-Glutamate is a potent neurotoxin, and the inadequate clearance of excitatory amino acids may contribute to the neurodegeneration seen in a variety of conditions, including epilepsy, ischemia, and amyotrophic lateral sclerosis. To establish the contributions of carrier systems to the etiology of neurological disorders, and to consider their potential utility as therapeutic targets, a detailed understanding of transporter function and pharmacology is required. This review summarizes current knowledge of the structural and functional diversity of excitatory amino acid transporters and explores how they might serve as targets for drug design.
The Impact of Genomics-Based Technologies on Drug Safety Evaluation
Authors: Waring Jeffrey F. , Ulrich Roger G.
Published: July 2002

Determining the potential toxicity of compounds early in the drug discovery process can be extremely beneficial in terms of both time and money conservation. Because of the speed of modern chemical synthesis and screening, to accurately evaluate the large number of compounds being produced, toxicology assays must have both high-fidelity and high-throughput capabilities. In addition, assays must be performed using limited amounts of compound. In the past decade, several new and innovative techniques have been developed that not only allow for high-throughput screening but can also provide detailed information concerning the molecular mechanisms behind toxic effects. Techniques such as hybridization microarrays, real-time polymerase chain reaction, and large-scale sequencing are some of the methods that have been or are starting to be used routinely in pharmaceutical companies. This review examines the contributions of these and related techniques toward toxicity evaluation of potential drug candidates and their future role in the discovery of new therapeutics.
STATE-TO-STATE CHEMICAL REACTION DYNAMICS IN POLYATOMIC SYSTEMS: Case Studies
Authors: Valentini James J
Published: July 2002

▪ Abstract  This review illustrates the experimental study of chemical reaction dynamics using methods that select the quantum states and energy of the reactants and determine the quantum states and energy of the products. The focus is reaction dynamics in systems in which at least one of the reactants or products is a polyatomic molecule. The approach taken is to select four prototype reaction systems as case studies to demonstrate the detail of information and insight that can come from such experiments. Thus, the review is selective and neither claims nor attempts to be comprehensive. Reference to and discussion of theoretical reaction dynamics are included where computational results directly connect with the experiments.
ROUTES AND MECHANISM OF FLUID TRANSPORT BY EPITHELIA
Authors: Spring Kenneth R.
Published: July 2002

▪ Abstract  The mechanism of fluid transport by leaky epithelia and the route taken by the transported fluid are in dispute. A consideration of current mathematical models for coupling of solutes and water, as well as the methodologies for the study of fluid transport, shows that local osmosis best accounts for water movement. Although it seems virtually certain that the tight junctions are water permeable, the fraction of absorbed fluid that crosses the tight junction cannot yet be determined with confidence.
NEMATODE MANAGEMENT IN SUSTAINABLE AND SUBSISTENCE AGRICULTURE
Authors: Bridge J.
Published: July 2002

▪ Abstract  In small-scale, subsistence agriculture in the tropics and the subtropics, traditional farming practices have evolved that provide a sustainable means of reducing the incidence and damage caused by pests including nematodes. Other newer, cultural and low-input practices can also be successfully introduced in small-scale farming. In sustainable and subsistence farming systems, nematodes and some other pests can be managed by integrating different farming practices into four strategies: preventing the introduction and spread of nematodes; using direct, nonchemical, cultural and physical control methods; encouraging naturally occurring biological control agents; and maintaining or enhancing the biodiversity inherent in multiple cropping and multiple cultivar traditional farming systems to increase the available resistance or tolerance to nematodes.
PHYTOALEXINS: What Have We Learned After 60 Years?
Authors: Hammerschmidt Ray
Published: July 2002

▪ Abstract  One of the best and longest-studied defense response of plants to infection is the induced accumulation of antimicrobial, low-molecular-weight secondary metabolites known as phytoalexins. Since the phytoalexin hypothesis was first proposed in 1940, a role for these compounds in defense has been revealed through several experimental approaches. Support has come, for example, through studies on the rate of phytoalexins in relation to cessation of pathogen development, quantification of phytoalexins at the infection site, and relationship of pathogen virulence to the phytoalexin tolerance. Evidence in support of phytoalexins in resistance as well some recent advances in phytoalexin biosynthesis are reviewed. Criteria for evaluating a role for phytoalexins in disease resistance are also discussed.
Lessons in Environmental Health in the Twentieth Century
Authors: Gochfeld Michael , Goldstein Bernard D.
Published: July 2002

▪ Abstract  Environmental health has evolved rapidly in recent decades, drawing largely on new analytic technologies, advanced data acquisition and modeling, mechanistic studies in toxicology, and the conceptual framework of risk assessment. The latter combines toxicologic and epidemiologic data with improved techniques for quantifying exposure, producing estimates of risks from environmental hazards or conditions to selected target populations. The public and governments have become increasingly concerned with environmental health and quality. The major lessons have been (a) environmental-health scientists must participate in policy debates; (b) environmental health problems are exceedingly complex and require interdisciplinary research; and (c) environmental health is a global issue. The globalization of commerce, the untested impact of international trade agreements, increased migration, and especially increased population, have profound impact on the quality as well as availability of air, water, land, and food. Global atmospheric transport of pollutants and the effect on atmosphere and climate are two examples of globalization of environmental health.
BRINGING EMOTIONS INTO SOCIAL EXCHANGE THEORY
Authors: Lawler Edward J. , Thye Shane R.
Published: July 2002

▪ Abstract  We analyze and review how research on emotion and emotional phenomena can elaborate and improve contemporary social exchange theory. After identifying six approaches from the psychology and sociology of emotion, we illustrate how these ideas bear on the context, process, and outcome of exchange in networks and groups. The paper reviews the current state of the field, develops testable hypotheses for empirical study, and provides specific suggestions for developing links between theories of emotion and theories of exchange.
Aging-Induced Phenotypic Changes and Oxidative Stress Impair Coronary Arteriolar Function
Authors: Csiszar Anna , Ungvari Zoltan , Edwards John G. , Kaminski Pawel , Wolin Michael S. , Koller Akos , Kaley Gabor
Published: July 2002

We aimed to elucidate the possible role of phenotypic alterations and oxidative stress in age-related endothelial dysfunction of coronary arterioles. Arterioles were isolated from the hearts of young adult (Y, 14 weeks) and aged (A, 80 weeks) male Sprague-Dawley rats. For videomicroscopy, pressure-induced tone of Y and A arterioles and their passive diameter did not differ significantly. In A, arterioles L-NAME (a NO synthase blocker)–sensitive flow-induced dilations were significantly impaired (Y: 41±8% versus A: 3±2%), which could be augmented by superoxide dismutase (SOD) or Tiron (but not
l
-arginine or the TXA
2
receptor antagonist SQ29,548). For lucigenin chemiluminescence, O
2
·−
generation was significantly greater in A than Y vessels and could be inhibited with SOD and diphenyliodonium. NADH-driven O
2
·−
generation was also greater in A vessels. Both endothelial and smooth muscle cells of A vessels produced O
2
·−
(shown with ethidium bromide fluorescence). For Western blotting, expression of eNOS and COX-1 was decreased in A compared with Y arterioles, whereas expressions of COX-2, Cu/Zn-SOD, Mn-SOD, xanthine oxidase, and the NAD(P)H oxidase subunits p47

phox

, p67

phox

, Mox-1, and p22

phox

did not differ. Aged arterioles showed an increased expression of iNOS, confined to the endothelium. Decreased eNOS mRNA and increased iNOS mRNA expression in A vessels was shown by quantitative RT-PCR. In vivo formation of peroxynitrite was evidenced by Western blotting, and immunohistochemistry showing increased 3-nitrotyrosine content in A vessels. Thus, aging induces changes in the phenotype of coronary arterioles that could contribute to the development of oxidative stress, which impairs NO-mediated dilations.
Insulin-Like Growth Factor-1 Enhances Inflammatory Responses in Endothelial Cells
Authors: Che Wenyi , Lerner-Marmarosh Nicole , Huang Qunhua , Osawa Masaki , Ohta Shinsuke , Yoshizumi Masanori , Glassman Michael , Lee Jiing-Dwan , Yan Chen , Berk Bradford C. , Abe Jun-ichi
Published: July 2002

Insulin-like growth factor (IGF)-1 and the type I IGF-1 receptor are important regulators of vascular function that may contribute to cardiovascular disease. We hypothesized that IGF-1 causes endothelial cell dysfunction and expression of neutrophil and monocyte adhesion molecules by enhancing pro-inflammatory cytokine signal transduction. Long-term IGF-1 treatment of endothelial cells potentiated c-Jun and nuclear factor NF-κB activation by tumor necrosis factor (TNF)-α and enhanced TNF-α–mediated adhesion molecule expression. In response to IGF-1 treatment, the expression of kinases in the c-Jun/c-Jun NH
2
-terminal kinase signaling pathway (MEKK1, MEK4, and JNK1/2) was unchanged, but expressions of insulin receptor substrate-1 and Grb2-associated binder-1 (Gab1) were significantly decreased. Because Gab1 is involved in both c-Jun and NF-κB activation by TNF-α, we focused on Gab1-dependent signaling. Gab1 inhibited c-Jun and NF-κB transcriptional activation by TNF-α. Interestingly, Gab1 inhibited c-Jun transcriptional activity induced by MEKK3 but not MEKK1 and MEK4. Gab1 associated with MEKK3, and a catalytically inactive form of MEKK3 inhibited TNF-α–induced c-Jun and NF-κB transcriptional activation, suggesting a critical role for Gab1 and MEKK3 in TNF-α signaling. These data demonstrate that Gab1 and MEKK3 play important roles in endothelial cell inflammation via regulating the activation of c-Jun and NF-κB. Furthermore, the IGF-1–mediated downregulation of Gab1 expression represents a novel mechanism to promote vascular inflammation and atherosclerosis.
Neuroprotection and P450 2C11 Upregulation After Experimental Transient Ischemic Attack
Authors: Alkayed Nabil J. , Goyagi Toru , Joh Hung-Dong , Klaus Judith , Harder David R. , Traystman Richard J. , Hurn Patricia D.
Published: July 2002

Background and Purpose

—

Transient ischemic attack (TIA) is a risk factor for stroke. However, TIA may also serve as a preconditioning stimulus, reducing damage from subsequent stroke. We tested the hypothesis that experimental TIA induces expression of P450 2C11, an arachidonic acid epoxygenase that produces vasodilator epoxyeicosatrienoic acids, leading to increased tissue perfusion and reduced stroke damage.

Methods

—

Wistar rats underwent three 10-minute middle cerebral artery occlusions (TIA) or sham surgery. Three days later, animals were subjected to 2-hour middle cerebral artery occlusion and 24 hours of reperfusion. Brains were stained with 2,3,5-triphenyltetrazolium chloride for infarct size measurement or processed for quantification of P450 2C11 mRNA and protein with the use of RNase protection assay and Western blotting. Regional cerebral blood flow (CBF) at the end of 2-hour ischemia was measured in separate groups of rats with iodoantipyrine autoradiography.

Results

—

Cerebral infarct was reduced by >50% in TIA- versus sham-preconditioned animals. 2C11 mRNA and protein were increased in ipsilateral hemisphere by 3 days after TIA but not sham surgery. Induction of 2C11 by TIA was also evident in ipsilateral hemisphere at 24 hours after 2-hour middle cerebral artery occlusion and 24 hours of reperfusion. End-ischemic regional CBF was not different between TIA- and sham-pretreated groups.

Conclusions

—

We conclude that experimental TIA induces ischemic tolerance by a mechanism temporally linked to upregulation of P450 2C11. Enzyme induction does not attenuate ischemic severity by amplifying end-ischemic CBF.
Integrated Care Pathways and Quality of Life on a Stroke Rehabilitation Unit
Authors: Sulch David , Melbourn Anne , Perez Inigo , Kalra Lalit
Published: July 2002

Background and Purpose

—

Integrated care pathways (ICP) may not reduce disability, institutionalization, or duration of hospitalization compared with conventional multidisciplinary team (MDT) care in organized stroke rehabilitation. Their potential to improve patient heath status or satisfaction with care is not known.

Methods

—

A comparison of quality of life, caregiver strain, and patient/caregiver satisfaction at 6 months after stroke was undertaken in 152 stroke patients randomized to receive ICP or MDT care. Differences in processes of care were recorded with the use of a predefined schedule. Multivariate analyses were undertaken to identify the effect of age, sex, stroke severity, functional status, mood, and use of care pathway on quality of life score.

Results

—

The 2 groups were comparable for baseline characteristics of age, sex, stroke severity, and initial disability. MDT care was characterized by greater emphasis on return of higher function and caregiver needs compared with ICP. EuroQol Visual Analogue Scale (EQ-VAS) scores were higher in the MDT group (median, 72 versus 63;
P
<0.005), who also had higher scores for EuroQol dimension of social functioning (
P
=0.014). Higher EQ-VAS scores were independently related to MDT care (
P
=0.04), Rankin score (
P
=0.01), and psychological function (
P
<0.0001) but not to age, sex, or stroke severity. There were no significant differences in patient or caregiver satisfaction between the 2 settings.

Conclusions

—

Better quality of life in patients receiving conventional MDT care may be attributable to improved social functioning and greater attention to higher function and caregiver needs during rehabilitation.
Domestic Responses to Capital Market Internationalization Under the Gold Standard, 1870–1914
Authors: Verdier Daniel
Published: July 2002

The internationalization of capital markets that occurred during the era of the classical gold standard (1870-1914) was part of a broader set of trends that threatened to drain local markets from capital and channel that capital to the national financial center and, from there, toward other national financial centers. Still, internationalization was neither inevitable, uniform, nor irreversible but was a political choice informed by redistributional considerations between rival domestic interests and decided by politically dominant coalitions. The domestic institutional structure in each country determined the composition of the politically dominant coalition. Decentralized structures allowed potential losers to curb public policies favorable to capital market internationalization, whereas centralized structures allowed expected winners to promote such policies. As a result, economies with centralized states ended up being the most dependent on the international capital market, whereas economies with decentralized states took a less active part in the globalization of finance.
In the Shadow of the Vote? Decision Making in the European Community
Authors: Golub Jonathan
Published: July 2002

Scholarship on the European Community (EC) focuses particular attention on how formal voting rules and institutional reform condition decision-making outcomes. The predominant view of EC history holds that decision making remained paralyzed until institutional reforms in 1987 and 1992 restored and expanded adherence to majority voting rules, which in turn unblocked and expedited EC legislative efforts. In this study I challenge these fundamental assumptions using comprehensive data for 1974–95 and a series of quantitative assessments, including event history analysis. I show that decision making in the 1970s was anything but paralyzed, that the impact of the Luxembourg Compromise has been greatly overstated, that institutional reforms actually encumbered rather than eased the EC legislative process, and that institutional effects are mediated by the underlying distribution of member state preferences. The findings have important implications for our understanding of the history and future trajectory of European integration and highlight the applicability of standard political science theories and methods to the study of the EC.
Morals and Moral Regulation in Protestant France
Authors: Mentzer Raymond A.
Published: July 2002

The investigation by the consistory of the Reformed Church of Montauban of an unmarried pregnancy and attempted abortion in the sixteenth century offers important insights into moral and social relationships within the early modern European community. Though the effect of the consistory's activities on the lives of those that it sought to discipline ought not be overestimated (intrusive as those activities might be by modern standards), a close reading of the narrative embedded in the consistorial records provides a valuable understanding of the Protestant church's role in reordering traditional attitudes and everyday behavior.
Towards an Immersive Intelligence
Authors: Nechvatal Joseph
Published: July 2002

This essay is an investigation into the immersive cultural consciousness that emerges from an immersive “optic” central to virtual reality. There seems to be a correlation between immersive ideals and desires for extrasensory, distributed disembodiment, meaning a loss of cognitive body-image involving the expansion of boundaries. Immersive art fulfills the prosthetic task of artificially facilitating such an unrestricted state. The desire to exist in an anti-mechanistic state of expansion is temporarily and symbolically realized in engaging immersive art. In virtual immersion, conventional optic models may be surpassed.
The Subject-in-Situ Generalization and the Role of Case in Driving Computations
Authors: Alexiadou Artemis , Anagnostopoulou Elena
Published: July 2002

The article establishes a novel generalization concerning the placement of arguments by Spell-Out. It centers on the principles that force arguments to leave the VP across languages. The empirical domain consists of constructions where subject movement is not required for reasons that have to do with the Extended Projection Principle. In these environments and whenever a sentence contains both a subject and a direct object, one of the arguments must vacate the VP. We argue that argument externalization is related to Case. It is forced because movement of both arguments to a single head T0 that contains two active Case features in the covert component is banned.
An Empirically Based System for Processing Definite Descriptions
Authors: Vieira Renata , Poesio Massimo
Published: July 2002

We present an implemented system for processing definite descriptions in arbitrary domains. The design of the system is based on the results of a corpus analysis previously reported, which highlighted the prevalence of discourse-new descriptions in newspaper corpora. The annotated corpus was used to extensively evaluate the proposed techniques for matching definite descriptions with their antecedents, discourse segmentation, recognizing discourse-new descriptions, and suggesting anchors for bridging descriptions.
Viewpoint Dependency in Visual Object Recognition Does Not Necessarily Imply Viewer-Centered Representation
Authors: Bar Moshe
Published: July 2002

The nature of visual object representation in the brain is the subject of a prolonged debate. One set of theories asserts that objects are represented by their structural description and the representation is “object-centered.” Theories from the other side of the debate suggest that humans store multiple “snapshots” for each object, depicting it as seen under various conditions, and the representation is therefore “viewer-centered.” The principal tool that has been used to support and criticize each of these hypotheses is subjects' performance in recognizing objects under novel viewing conditions. For example, if subjects take more time in recognizing an object from an unfamiliar viewpoint, it is common to claim that the representation of that object is viewpoint-dependent and therefore viewer-centered. It is suggested here, however, that performance cost in recognition of objects under novel conditions may be misleading when studying the nature of object representation. Specifically, it is argued that viewpoint-dependent performance is not necessarily an indication of viewer-centered representation. An account for the neural basis of perceptual priming is first provided. In light of this account, it is conceivable that viewpoint dependency reflects the utilization of neural paths with different levels of sensitivity en route to the same representation, rather than the existence of viewpoint-specific representations. New experimental paradigms are required to study the validity of the viewer-centered approach.
Does the Medial Temporal Lobe Bind Phonological Memories?
Authors: Knott Raymond , Marslen-Wilson William
Published: July 2002

The medial temporal lobes play a central role in the consolidation of new memories. Medial temporal lesions impair episodic learning in amnesia, and disrupt vocabulary acquisition. To investigate the role of consolidation processes in phonological memory and to understand where and how, in amnesia, these processes begin to fail, we reexamined phonological memory in the amnesic patient HM. While HM's word span performance was normal, his supraspan recall was shown to be markedly impaired, with his recall characterized by a distinctive pattern of phonological errors, where he recombined phonemes from the original list to form new response words. These were similar to errors observed earlier for patients with specifically semantic deficits. Amnesic Korsakoff's patients showed a similar, though much less marked, pattern. We interpret the data in terms of a model of lexical representation where temporal lobe damage disrupts the processes that normally bind semantic and phonological representations.
Effects of Syntactic Structure and Propositional Number on Patterns of Regional Cerebral Blood Flow
Authors: Caplan David , Alpert Nathaniel , Waters Gloria
Published: July 2002

Positron emission tomography (PET) was used to determine regional cerebral blood flow (rCBF) as a function of the syntactic form and propositional density of sentences. rCBF increased in the left pars opercularis, part of Broca's area, when subjects processed syntactically more complex sentences. There were no differences in rCBF in the perisylvian association cortex traditionally associated with language processing when subjects made plausibility judgments about sentences with two propositions as compared to sentences with one proposition, but rCBF increased in infero-posterior brain regions. These results suggest that there is a specialization of neural tissue in Broca's area for constructing aspects of the syntactic form of sentences to determine sentence meaning. They also suggest that this specialization is separate from the brain systems that are involved in utilizing the meaning of a sentence that has been understood to accomplish a task.
Spatial S-R Compatibility with Centrally Presented Stimuli: An Event-Related Asymmetry Study on Dimensional Overlap
Authors: Wascher Edmund , Reinhard Meike , Wauschkuhn Bernd , Verleger Rolf
Published: July 2002

Lateral presentation of relevant information facilitates manual responses if the side of relevant information corresponds to the side of the response. Recently, temporally overlapping EEG asymmetries over the central motor cortex and posterior sites were reported as a possible correlate of the sensory-motor integration of spatial information. The present study investigated whether sensory-motor integration of spatial information can occur with symbolic spatial information the same way as with laterally presented stimuli. The task required participants to respond to arrows (target stimuli), which were “flanked” (from above and below) by neutral stimuli or by other arrows (compatible or not). In Experiment 1, this task was compared to the same task with letters as stimuli and to an incompatible task where participants had to respond “against” the arrow direction. The effect of the flankers on response times was largest if subjects had to respond to the arrows in the common way. This was also the only task of Experiment 1 for which marked EEG asymmetries related to the direction of the flankers were observed. In Experiment 2, the onsets of target stimulus and flankers differed in time. Event-related lateralizations of the EEG over sensory and primary motor areas—as a lateralized readiness potential—were always, apparently automatically, evoked by flanking arrows, indicating automatic response activation evoked by symbolic spatial information. In accordance to recent theories of temporally decaying response activation, manual responses were affected only if the target was either shortly preceded by or appeared simultaneously with the flankers. The temporal overlap of EEG asymmetries related to direction encoding, automatic response activation, and to response preparation indicated that a widespread cortical network is activated by any salient directional information that enables subjects to respond quickly if the directional code of the stimulus overlaps with the directional code of the response.
Activation of Cortical and Cerebellar Motor Areas during Executed and Imagined Hand Movements: An fMRI Study
Authors: Lotze Martin , Montoya Pedro , Erb Michael , Hülsmann Ernst , Flor Herta , Klose Uwe , Birbaumer Niels , Grodd Wolfgang
Published: July 2002

Brain activation during executed (EM) and imagined movements (IM) of the right and left hand was studied in 10 healthy right-handed subjects using functional magnetic resonance imagining (fMRI). Low electromyographic (EMG) activity of the musculi flexor digitorum superficialis and high vividness of the imagined movements were trained prior to image acquisition. Regional cerebral activation was measured by fMRI during EM and IM and compared to resting conditions. Anatomically selected regions of interest (ROIs) were marked interactively over the entire brain. In each ROI activated pixels above a t value of 2.45 (p < 0.01) were counted and analyzed. In all subjects the supplementary motor area (SMA), the premotor cortex (PMC), and the primary motor cortex (M1) showed significant activation during both EM and IM; the somatosensory cortex (S1) was significantly activated only during EM. Ipsilateral cerebellar activation was decreased during IM compared to EM. In the cerebellum, IM and EM differed in their foci of maximal activation: Highest ipsilateral activation of the cerebellum was observed in the anterior lobe (Larsell lobule H IV) during EM, whereas a lower maximum was found about 2-cm dorsolateral (Larsell lobule H VII) during IM. The prefrontal and parietal regions revealed no significant changes during both conditions. The results of cortical activity support the hypothesis that motor imagery and motor performance possess similar neural substrates. The differential activation in the cerebellum during EM and IM is in accordance with the assumption that the posterior cerebellum is involved in the inhibition of movement execution during imagination.
Practical Identifiability of Finite Mixtures of Multivariate Bernoulli Distributions
Authors: Carreira-Perpiñán Miguel Á. , Renals Steve
Published: July 2002

The class of finite mixtures of multivariate Bernoulli distributions is known to be nonidentifiable; that is, different values of the mixture parameters can correspond to exactly the same probability distribution. In principle, this would mean that sample estimates using this model would give rise to different interpretations. We give empirical support to the fact that estimation of this class of mixtures can still produce meaningful results in practice, thus lessening the importance of the identifiability problem. We also show that the expectation-maximization algorithm is guaranteed to converge to a proper maximum likelihood estimate, owing to a property of the log-likelihood surface. Experiments with synthetic data sets show that an original generating distribution can be estimated from a sample. Experiments with an electropalatography data set show important structure in the data.
Resampling Method for Unsupervised Estimation of Cluster Validity
Authors: Levine Erel , Domany Eytan
Published: July 2002

We introduce a method for validation of results obtained by clustering analysis of data. The method is based on resampling the available data. A figure of merit that measures the stability of clustering solutions against resampling is introduced. Clusters that are stable against resampling give rise to local maxima of this figure of merit. This is presented first for a one-dimensional data set, for which an analytic approximation for the figure of merit is derived and compared with numerical measurements. Next, the applicability of the method is demonstrated for higher-dimensional data, including gene microarray expression data.
Receptive Field Formation in Natural Scene Environments: Comparison of Single-Cell Learning Rules
Authors: Blais Brian S. , Intrator N. , Shouval H. , Cooper Leon N.
Published: July 2002

We study several statistically and biologically motivated learning rules using the same visual environment: one made up of natural scenes and the same single-cell neuronal architecture. This allows us to concentrate on the feature extraction and neuronal coding properties of these rules. Included in these rules are kurtosis and skewness maximization, the quadratic form of the Bienenstock-Cooper-Munro (BCM) learning rule, and single-cell independent component analysis. Using a structure removal method, we demonstrate that receptive fields developed using these rules depend on a small portion of the distribution. We find that the quadratic form of the BCM rule behaves in a manner similar to a kurtosis maximization rule when the distribution contains kurtotic directions, although the BCM modification equations are computationally simpler.
On the Approximation Rate of Hierarchical Mixtures-of-Experts for Generalized Linear Models
Authors: Jiang Wenxin , Tanner Martin A.
Published: July 2002

We investigate a class of hierarchical mixtures-of-experts (HME) models where generalized linear models with nonlinear mean functions of the form ψ(α + xTβ) are mixed. Here ψ(·) is the inverse link function. It is shown that mixtures of such mean functions can approximate a class of smooth functions of the form ψ(h(x)), where h(·) ε W∞2;k (a Sobolev class over [0, 1]s, as the number of experts m in the network increases. An upper bound of the approximation rate is given as O(m−2/s) in Lp norm. This rate can be achieved within the family of HME structures with no more than s-layers, where s is the dimension of the predictor x.
Imaging Music: Abstract Expressionism and Free Improvisation
Authors: Sansom Matthew
Published: July 2002

The author defines free improvisation, a form of music-making that first emerged in the 1960s with U.K. composers and groups such as Cardew, Bailey, AMM and the Spontaneous Music Ensemble. The approach here considers free improvisation as creative activity, encompassing its artistic agenda on the one hand and the process-based dynamic of its production on the other. After considering the historical location of free improvisation within Western music history, the article explores free improvisation as analogous with Abstract Expressionist art. This comparison enables a fuller understanding of the activity's conceptual basis and the creative process it engenders.
Patterns of Network and User Activity in an Inhabited Television Event
Authors: Greenhalgh Chris , Benford Steve , Craven Mike
Published: July 2002

Inhabited television takes traditional broadcast television and combines it with multiuser virtual reality to give new possibilities for interaction and participation in and around shows or channels. Out of This World was an experimental inhabited TV show, staged in Manchester in September of 1998, using the MASSIVE-2 system. During this event, we captured comprehensive records of network traffic and additional logs of user activity (in particular, movement and speaking). In this paper, we present the results of our analyses of network and user activity in these shows. We contrast our results with those obtained from previous analyses of teleconferencing-style scenarios. We find that the inhabited television scenario results in much higher levels of user activity and significant bursts of coordinated activity. We show how these characteristics must be taken into account when designing a system and infrastructure for applications of this kind. In particular, it is clear that any notion of strict turn-taking (and associated assumptions about resource sharing) is completely unfounded in this domain. We also show that the concept of “levels of participation” is a powerful tool for understanding and managing the bandwidth requirements of an inhabited television event.
Identifying Likely Successful Users of Virtual Reality Systems
Authors: Howe Tim , Sharkey Paul M.
Published: July 2002

This paper suggests a method for identifying individuals who are most suited to using virtual reality (VR) systems. The aim is to help both an individual or employer to decide where that individual's skills and abilities would be best deployed. By considering a potential user's competence and temperament, a graphical representation is introduced that may then be used to crudely delineate a high-aptitude participant against those with lesser capabilities. By introducing standard tests for competence and a standard classifier for temperament, and by further weighting each measure with respect to the technology currently available and the application, a detailed representation of the effectiveness of different users is developed.
The Effects of Proprioceptive and Visual Feedback on Geographical Orientation in Virtual Environments
Authors: Bakker Niels H. , Werkhoven Peter J. , Passenier Peter O.
Published: July 2002

To effectively use a virtual environment (VE) for applications such as training and design evaluation, a good sense of orientation is needed in the VE. “Natural” human geographical orientation, when moving around in the world, relies on visual as well as proprioceptive feedback. However, the present navigation metaphors that are used to move around in the VE often lack proprioceptive feedback. To investigate the possible consequences this may have, an experiment was conducted on the relative contributions of visual and proprioceptive feedback on path integration in VE. Subjects were immersed in a virtual forest and were asked to turn specific angles under different combinations of visual, vestibular, and kinesthetic feedback (pure visual, visual plus vestibular, visual plus vestibular plus kinesthetic, pure vestibular, and vestibular plus kinesthetic). Furthermore, two visual conditions with different visual flows were tested: normal visual flow and decreased visual flow provided by a 60% zoom. Results show that kinesthetic feedback provides the most reliable and accurate source of information to use for path integration, indicating the benefits of incorporating this kind of feedback in navigation metaphors. Orientation based on visual flow alone is most inaccurate and unreliable. In all conditions, subjects overestimated their turning speed and subsequently didn't turn far enough. Both the absolute errors and the variation in path integration increase with the length of the path.
Automatic Identification of Environment Haptic Properties
Authors: Dupont Pierre E. , Schulteis Capt. Timothy M. , Millman Paul A. , Howe Robert D.
Published: July 2002

Many applications can be imagined for a system that processes sensory information collected during telemanipulation tasks in order to automatically identify properties of the remote environment. These applications include generating model-based simulations for training operators in critical procedures and improving real-time performance in unstructured environments or when time delays are large. This paper explores the research issues involved in developing such an identification system, focusing on properties that can be identified from remote manipulator motion and force data. As a case study, a simple block-stacking task, performed with a teleoperated two-fingered planar hand, is considered. An algorithm is presented that automatically segments the data collected during the task, given only a general description of the temporal sequence of task events. Using the segmented data, the algorithm then successfully estimates the weight, width, height, and coefficient of friction of the two blocks handled during the task. This data is used to calibrate a virtual model incorporating visual and haptic feedback. This case study highlights the broader research issues that must be addressed in automatic property identification.