bluuebunny/crossref_metadata_2025 huggingface dataset:
Orchestrated Information Transfer Underlying Leukocyte Endothelial Interactions
Authors: Ebnet Klaus , Kaldjian Eric P. , Anderson Arthur O. , Shaw Stephen
Published: July 2002

The specificity and efficiency of leukocyte binding to endothelial cells (ECs) depends on coordinated information transfer from the underlying tissue to endothelium and from there to the leukocyte. We address three distinct information-transfer points in this system: 1. How does the leukocyte read information from the EC? This process is best accounted for by the paradigm of a multi-step adhesion cascade optimized for rapid information readout; it consists of primary adhesion (rolling/tethering), triggering, and strong adhesion. Recent studies with T cells, monocytes, and eosinophils confirm the generality of the paradigm. The concept of primary adhesion has been expanded to involve not only the selectins, but also certain integrins; furthermore, it depends on receptor concentration on leukocyte microvilli. 2. What information from the underlying tissue does the EC transform into signals for the leukocytes? And what rules govern that process? We illustrate the principles with chemokines, believed to participate in the triggering step. The endothelium displays chemokines either (a) directly by “posting” them from other cells or (b) by integrating a variety of tissue and environmental signals and “relaying” that information by producing its own chemokines and surface adhesion molecules. The rules for this endothelial transduction include specificity coupled with redundancy, amplification, synergy, and coordinated induction of ensembles of molecules. Finally, 3. How does the relevant information reach the endothelium? Simple diffusion is sufficient to deliver signals from cells close to the vessel. However, longer range soluble mediator transport appears to be facilitated by fiber bundles, particularly those ensheathed by fibroblastic reticular cells in the lymph node.
TRANSPLANTATION OF THE HEART AND LUNGS IN CHILDREN
Authors: Spray, M.D Thomas L.
Published: July 2002

▪ Abstract  Heart transplantation in children with complex congenital heart disease or cardiomyopathies has become an effective form of therapy for patients with no other surgical options. Because pediatric pulmonary transplantation is a relatively new procedure, long-term follow-up data are not yet available. However, the intermediate-term results of pediatric lung transplantation appear similar to those for heart and lung transplantation. Children represent a particularly difficult patient group for transplant of thoracic organs, and recipients must be selected carefully. Additionally, physicians must pay close attention to multiple medical conditions relating to the underlying disease process in order to achieve optimal results.
THE CARDIAC ION CHANNELS: Relevance to Management of Arrhythmias
Authors: Roden, M.D Dan M. , George Alfred L.
Published: July 2002

▪ Abstract  The electrical activity of cardiac tissue is determined by the highly regulated flow of ions across the cell membrane during the cardiac action potential. Ion channels are pore-forming proteins through which these electric currents flow. In this review, the ion currents that underlie the action potential are first described. Then, the way in which expression of individual ion-channel genes results in such ion currents is discussed. Finally, the concept that arrhythmias may be due to abnormalities of structure, function, or number of ion channels, or the way in which they respond to abnormalities in their environment (such as acute ischemia), is reviewed. Further understanding of the molecular mechanisms underlying normal and abnormal cardiac electrophysiologic behavior should allow the development of safer and more effective antiarrhythmic interventions.
Artificial Skin
Authors: Schulz III J. T. , Tompkins R. G. , Burke J. F.
Published: July 2002

▪ Abstract  The skin is a complex organ that is difficult to replace when it is irreversibly damaged by burns, trauma, or disease. Although autologous skin transplantation remains the most common form of treatment in patients with significant skin loss, there are now a number of commercially available products that can be used to replace the skin temporarily or permanently. Here we describe several such products under the rubric “artificial skin,” focusing on two types of technology that have been applied to the problem of permanent skin replacement.
Gene Transfer for Angiogenesis in Coronary Artery Disease
Authors: Laham Roger J. , Simons Michael , Sellke Frank
Published: July 2002

▪ Abstract  Angiogenesis is a promising novel therapeutic strategy to provide new venues for blood flow in patients with severe ischemic heart and peripheral vascular disease, who are not candidates for standard revascularization strategies. We describe the underlying mechanisms involved in physiologic and therapeutic angiogenesis, underscoring the relative importance of vasculogenesis, angiogenesis, and arteriogenesis. We then present the various gene transfer vectors including plasmid, viral, and cell-based vectors, and various delivery modalities. The available preclinical data are presented, followed by a description of preliminary clinical experience, with an emphasis on the preliminary nature of these results, which address safety and not efficacy. Finally, we discuss the promises and pitfalls of clinical angiogenesis and gene transfer studies, stressing the importance of proper design of clinical trials and adequate protection of research subjects.
Breast Cancer Risk Reduction: Strategies for Women at Increased Risk
Authors: Chlebowski Rowan T.
Published: July 2002

▪ Abstract  Breast cancer risk reduction now represents an achievable medical objective. Current interventions include selective estrogen receptor modulators (SERMs), prophylactic surgery, and lifestyle change. For SERMs, current evidence supports tamoxifen use for breast cancer risk reduction whereas raloxifene requires further study. Prophylactic mastectomy and prophylactic oophorectomy, effective in retrospective clinical experiences, should be considered only for women at substantial risk willing to accept the irreversible consequences of these procedures. Although dietary fat intake is under clinical trial evaluation, lifestyle change, including weight loss, dietary change, and increased physical activity, can be recommended based on other health considerations. Use of any intervention requires careful breast cancer risk assessment, risk-benefit calculations, and informed decision making with full patient participation. Future breast cancer risk assessment may incorporate additional biologic measures of estrogen exposure and/or analyses of collected breast cells. Under active evaluation are novel SERMs, aromatase inhibitors/inactivators, gonadotrophin-releasing hormone agonists, retinoids, statins, and tyrosine kinase and cyclooxygenase-2 inhibitors.
NUTRITIONAL CONSEQUENCES OF THE AFRICAN DIASPORA
Authors: Luke Amy , Cooper Richard S , Prewitt T Elaine , Adeyemo Adebowale A , Forrester Terrence E
Published: July 2002

▪ Abstract  Along with their foods and dietary customs, Africans were carried into diaspora throughout the Americas as a result of the European slave trade. Their descendants represent populations at varying stages of the nutrition transition. West Africans are in the early stage, where undernutrition and nutrient deficiencies are prevalent. Many Caribbean populations represent the middle stages, with undernutrition and obesity coexisting. African-Americans and black populations in the United Kingdom suffer from the consequences of caloric excess and diets high in fat and animal products. Obesity, non–insulin-dependent diabetes mellitus, hypertension, coronary heart disease, and certain cancers all follow an east-to-west gradient of increasing prevalence. Public health efforts must focus not only on eradicating undernutrition in West Africa and the Caribbean but also on preventing obesity, hypercholesterolemia, and their consequences. Fortunately, a coherent and well-supported set of recommendations exists to promote better nutrition. Implementation of it founders primarily as a result of the influence of commercial and political interests.
CYTOTOXICITY OF SHORT-CHAIN ALCOHOLS
Authors: Baker R. C. , Kramer R. E.
Published: July 2002

▪ Abstract  Ethanol and other short-chain alcohols elicit a number of cellular responses that are potentially cytotoxic and, to some extent, independent of cell type. Aberrations in phospholipid and fatty acid metabolism, changes in the cellular redox state, disruptions of the energy state, and increased production of reactive oxygen metabolites have been implicated in cellular damage resulting from acute or chronic exposure to short-chain alcohols. Resulting disruptions of intracellular signaling cascades through interference with the synthesis of phosphatidic acid, decreases in phosphorylation potential and lipid peroxidation are mechanisms by which solvent alcohols can affect the rate of cell proliferation and, consequently, cell number. Nonoxidative metabolism of short-chain alcohols, including phospholipase D–mediated synthesis of alcohol phospholipids, and the synthesis of fatty acid alcohol esters are additional mechanisms by which alcohols can affect membrane structure and compromise cell function.
HIGH RESOLUTION SPECTROSCOPY IN THE GAS PHASE: Even Large Molecules Have Well-Defined Shapes
Authors: Pratt David W.
Published: July 2002

▪ Abstract  A review of recent high-resolution microwave, infrared, and optical spectroscopy experiments demonstrates that remarkable progress has been made in the past 20 years in determining the equilibrium geometries of large polyatomic molecules and their clusters in the gas phase, and how these geometries change when the photon is absorbed. A special focus is on the dynamical information that can be obtained from such studies, particularly of electronically excited states.
Renal Genetic Disorders Related to K+ and Mg2+
Authors: Warnock David G.
Published: July 2002

▪ Abstract  The recent knowledge of the renal epithelial transport systems has exploded with the identification, cloning, and characterization of a large number of membrane transport proteins. The fundamental aspects of these transporters are beginning to emerge at the molecular level and are summarized in the accompanying contributions in this volume of the Annual Review of Physiology. The aim of my review is to integrate this body of knowledge with the understanding of the clinical disorders of human mineral homeostasis that accompany gain, loss, or dysregulation of function of these transport systems. The specific focus is on the best defined human clinical syndromes in which there are derangements in K+ and Mg2+ homeostasis.
THE CAENORHABDITIS ELEGANS GENOME: A Guide in The Post Genomics Age
Authors: Bird David McK , Opperman Charles H , Jones Steven JM , Baillie David L
Published: July 2002

▪ Abstract  The completion of the entire genome sequence of the free-living nematode, Caenorhabditis elegans is a tremendous milestone in modern biology. Not only will scientists be poring over data mined from this resource, but techniques and methodologies developed along the way have changed the way we can approach biological questions. The completion of the C. elegans genomic sequence will be of particular importance to scientists working on parasitic nematodes. In many cases, these nematode species present intractable challenges to those interested in their biology and genetics. The data already compared from parasites to the C. elegans database reveals a wealth of opportunities for parasite biologists. It is likely that many of the same genes will be present in parasites and that these genes will have similar functions. Additional information regarding differences between free-living and parasitic species will provide insight into the evolution and nature of parasitism. Finally, genetic and genomic approaches to the study of parasitic nematodes now have a clearly marked path to follow.
LESSONS FROM 12 YEARS OF COMPARATIVE RISK PROJECTS
Authors: Jones Ken , Klein Heidi
Published: July 2002

▪ Abstract  Can an analytical tool for comparing environmental risks and policy activities be used to evaluate their relative efficacy in ultimately changing the allocation of public funds? Some insight is possible through a review of comparative risk projects that have been carried out at the city, state, and national levels, as well as among Indian tribes, over the past 12 years. The lessons from this review should apply to the field of public health. For every comparison of environmental issues, such as clean-air standards with fish consumption advisories, there is a parallel discussion of public health priorities and strategies, such as antismoking and pregnancy prevention programs, immunization programs and disease surveillance efforts, or well-baby clinics and food safety programs. Lessons from comparative risk projects and processes may offer the public health community new ways of thinking about using stakeholder assessment processes in developing public health policy.
Plasma Homocysteine and Parental Myocardial Infarction in Young Adults in Jerusalem
Authors: Kark J.D. , Sinnreich R. , Rosenberg I.H. , Jacques P.F. , Selhub J.
Published: July 2002

Background

—

A causal role for mildly elevated plasma homocysteine (tHcy) in cardiovascular disease remains undetermined. To address the unresolved issue of the antecedent-consequent directionality of the relationship, we assessed the familial association of tHcy with parental myocardial infarction (MI) in young Israeli men and women. We also compared tHcy concentrations in Jerusalem, where rates of coronary heart disease (CHD) are high, with the United States Third National Health and Examination Survey (NHANES III).

Methods and Results

—

A total of 8646 17-year-olds and 6952 parents were examined from 1976 to 1979 in Jerusalem. At ages 28 to 32 years, offspring of parents who experienced a documented MI during a 10-year follow-up (n=133 men, 62 women; 72% response) and offspring of CHD-free parents (n=389 men, 208 women; 71% response) were reexamined. tHcy levels were determined by the same laboratory for the NHANES non-Hispanic white population aged 25 to 34 years (n=379) and the Jerusalem population sample (n=858). Men from Jerusalem, but not women, had clearly higher tHcy levels than the sample from the United States (90th percentile, 23 versus 14 μmol/L). This difference was largely attributable to lower plasma vitamin B
12
levels in the Israeli population. Male case offspring had higher adjusted tHcy than did controls (1.9 μmol/L,
P
=0.002). Logistic modeling revealed a graded increase in risk of parental MI across quintiles of offspring tHcy, with an adjusted odds ratio of 2.7 in the 5th quintile (
P
=0.0026 for trend).

Conclusions

—

The higher tHcy in young male offspring of parents with CHD suggests that elevated tHcy precedes manifestation of CHD. The elevated population tHcy in men may contribute to the high incidence of CHD in Israel.
Chlamydia pneumoniae
Seropositivity Is Associated With Increased Plasma Levels of Soluble Cellular Adhesion Molecules in Community-Dwelling Subjects
Authors: Kohara Katsuhiko , Tabara Yasuharu , Yamamoto Yoshikuni , Igase Michiya , Miki Tetsuro
Published: July 2002

Background and Purpose

—

In vitro studies have demonstrated that
Chlamydia pneumoniae
infection of the endothelium increases the expression of adhesion molecules and chemokines, indicating that
C pneumoniae
infection affects the adhesion and recruitment of leukocytes to the endothelium, which is believed to be involved in the initial steps of atherosclerosis. However, whether chronic
C pneumoniae
infection increases these molecules in vivo has not been elucidated.

Methods

—

The association between
C pneumoniae
seropositivity and plasma concentrations of soluble adhesion molecules and a chemokine was investigated in 200 community-dwelling residents free from cardiovascular diseases and medication. Plasma levels of IgA and IgG antibodies to
C pneumoniae
were measured by enzyme-linked immunosorbent assay. Indices of IgG and IgA antibodies were determined as the ratio to the standardized positive control. The subjects were divided into 3 groups according to the indices of antibodies:
C pneumoniae
seronegative (n=57, IgA<1.0 and IgG<1.0),
C pneumoniae
intermediate (n=81, 1.0≤IgA≥1.1 or 1.0≤IgG≥1.1), and
C pneumoniae
seropositive (n=62, IgA>1.1 and IgG>1.1). Plasma concentrations of soluble forms of intercellular adhesion molecule-1 (ICAM-1), vascular cellular adhesion molecule-1, and monocyte chemoattractant protein-1 were determined by enzyme-linked immunosorbent assay.

Results

—

Plasma concentrations of ICAM-1 (392±118, 398±94, 470±154 ng/mL,
P
=0.0004) and vascular cellular adhesion molecule-1 (402±146, 419±130, 472±181 ng/mL,
P
=0.03) were significantly different among the
C pneumoniae
seronegative, intermediate, and seropositive groups respectively. However, plasma monocyte chemoattractant protein-1 was not significantly different among the 3 groups. Stepwise regression analysis showed that plasma concentration of ICAM-1 was significantly associated with
C pneumoniae
seropositivity, independent of other known risk factors for atherosclerosis and carotid intima-media thickness.

Conclusion

—

These findings indicate that
C pneumoniae
seropositivity is associated with higher plasma concentrations of soluble forms of adhesion molecules in the general population. The increase in circulating adhesion molecules may underlie the mechanisms linking
C pneumoniae
infection and atherosclerosis in vivo.
Toward a Third Culture: Being In Between
Authors: Vesna Victoria
Published: July 2002

Artists working with technology are frequently informed and inspired by exciting scientific innovations, and often turn to contemporary philosophical interpretations of these events, which positions them in between the “two cultures,” a position that creates the potential for a “Third Culture,” as predicted by C.P. Snow himself. This emerging culture is not composed of the scientific elite as some propose, but will emerge out of triangulation of the arts, sciences and humanities. Although media artists are posed to play an important role in bridging the cultural and language gaps, this essay warns against adopting humanist interpretations of scientific work or taking for granted scientific assertions without active dialogue with both.
Projection and Phrase Structure
Authors: Brody Michael
Published: July 2002

Perfect Syntax dispenses with the idea of externally forced imperfections in syntax. This article presents a system of principles relating (L) LF representations and lexical items that aims to be compatible with this assumption. The core of this theory is that phrase structures are viewed as projection lines (lexical items and their projections) linked by an Insert relation. This explains uniqueness and locality of projection, the fact that phrases and nonphrasal elements can immediately dominate each other only when they are part of the same projection line, and most effects of the “target projects” requirement. I attribute a residue to the Generalized Projection Principle, for which I also provide an explanation. In addition, I explore various consequences of the present approach for the Move/Chain relation.
Estimating Functions of Independent Component Analysis for Temporally Correlated Signals
Authors: Amari Shun-ichi
Published: July 2002

This article studies a general theory of estimating functions of independent component analysis when the independent source signals are temporarily correlated. Estimating functions are used for deriving both batch and on-line learning algorithms, and they are applicable to blind cases where spatial and temporal probability structures of the sources are unknown. Most algorithms proposed so far can be analyzed in the framework of estimating functions. An admissible class of estimating functions is derived, and related efficient on-line learning algorithms are introduced. We analyze dynamical stability and statistical efficiency of these algorithms. Different from the independently and identically distributed case, the algorithms work even when only the second-order moments are used. The method of simultaneous diagonalization of cross-covariance matrices is also studied from the point of view of estimating functions.
Visualizing the Function Computed by a Feedforward Neural Network
Authors: Plate Tony A. , Bert Joel , Grace John , Band Pierre
Published: July 2002

A method for visualizing the function computed by a feedforward neural network is presented. It is most suitable for models with continuous inputs and a small number of outputs, where the output function is reasonably smooth, as in regression and probabilistic classification tasks. The visualization makes readily apparent the effects of each input and the way in which the functions deviate from a linear function. The visualization can also assist in identifying interactions in the fitted model. The method uses only the input-output relationship and thus can be applied to any predictive statistical model, including bagged and committee models, which are otherwise difficult to interpret. The visualization method is demonstrated on a neural network model of how the risk of lung cancer is affected by smoking and drinking.
Impact of Correlated Inputs on the Output of the Integrate-and-Fire Model
Authors: Feng Jianfeng , Brown David
Published: July 2002

For the integrate-and-fire model with or without reversal potentials, we consider how correlated inputs affect the variability of cellular output. For both models, the variability of efferent spike trains measured by coefficient of variation (CV) of the interspike interval is a nondecreasing function of input correlation. When the correlation coefficient is greater than 0.09, the CV of the integrate-and-fire model without reversal potentials is always above 0.5, no matter how strong the inhibitory inputs. When the correlation coefficient is greater than 0.05, CV for the integrate- and-fire model with reversal potentials is always above 0.5, independent of the strength of the inhibitory inputs. Under a given condition on correlation coefficients, we find that correlated Poisson processes can be decomposed into independent Poisson processes. We also develop a novel method to estimate the distribution density of the first passage time of the integrate-and-fire model.
The Limits of Counting Accuracy in Distributed Neural Representations
Authors: Gardner-Medwin A. R. , Barlow H. B.
Published: July 2002

Learning about a causal or statistical association depends on comparing frequencies of joint occurrence with frequencies expected from separate occurrences, and to do this, events must somehow be counted. Physiological mechanisms can easily generate the necessary measures if there is a direct, one-to-one relationship between significant events and neural activity, but if the events are represented across cell populations in a distributed manner, the counting of one event will be interfered with by the occurrence of others. Although the mean interference can be allowed for, there is inevitably an increase in the variance of frequency estimates that results in the need for extra data to achieve reliable learning. This lowering of statistical efficiency (Fisher, 1925) is calculated as the ratio of the minimum to actual variance of the estimates. We define two neural models, based on presynaptic and Hebbian synaptic modification, and explore the effects of sparse coding and the relative frequencies of events on the efficiency of frequency estimates. High counting efficiency must be a desirable feature of biological representations, but the results show that the number of events that can be counted simultaneously with 50% efficiency is fewer than the number of cells or 0.1-0.25 of the number of synapses (on the two models)—many fewer than can be unambiguously represented. Direct representations would lead to greater counting efficiency, but distributed representations have the versatility of detecting and counting many unforeseen or rare events. Efficient counting of rare but important events requires that they engage more active cells than common or unimportant ones. The results suggest reasons that representations in the cerebral cortex appear to use extravagant numbers of cells and modular organization, and they emphasize the importance of neuronal trigger features and the phenomena of habituation and attention.
A Constrained EM Algorithm for Independent Component Analysis
Authors: Welling Max , Weber Markus
Published: July 2002

We introduce a novel way of performing independent component analysis using a constrained version of the expectation-maximization (EM) algorithm. The source distributions are modeled as D one-dimensional mixtures of gaussians. The observed data are modeled as linear mixtures of the sources with additive, isotropic noise. This generative model is fit to the data using constrained EM. The simpler “soft-switching” approach is introduced, which uses only one parameter to decide on the sub- or supergaussian nature of the sources. We explain how our approach relates to independent factor analysis.
Binding and Normalization of Binary Sparse Distributed Representations by Context-Dependent Thinning
Authors: Rachkovskij Dmitri A. , Kussul Ernst M.
Published: July 2002

Distributed representations were often criticized as inappropriate for encoding of data with a complex structure. However Plate's holographic reduced representations and Kanerva's binary spatter codes are recent schemes that allow on-the-fly encoding of nested compositional structures by real-valued or dense binary vectors of fixed dimensionality.

In this article we consider procedures of the context-dependent thinning developed for representation of complex hierarchical items in the architecture of associative-projective neural networks. These procedures provide binding of items represented by sparse binary codevectors (with low probability of 1s). Such an encoding is biologically plausible and allows a high storage capacity of distributed associative memory where the codevectors may be stored.

In contrast to known binding procedures, context-dependent thinning preserves the same low density (or sparseness) of the bound codevector for a varied number of component codevectors. Besides, a bound codevector is similar not only to another one with similar component codevectors (as in other schemes) but also to the component codevectors themselves. This allows the similarity of structures to be estimated by the overlap of their codevectors, without retrieval of the component codevectors. This also allows easy retrieval of the component codevectors.

Examples of algorithmic and neural network implementations of the thinning procedures are considered. We also present representation examples for various types of nested structured data (propositions using role filler and predicate arguments schemes, trees, and directed acyclic graphs) using sparse codevectors of fixed dimension. Such representations may provide a fruitful alternative to the symbolic representations of traditional artificial intelligence as well as to the localist and microfeature-based connectionist representations.
Optimal Smoothing in Visual Motion Perception
Authors: Rao Rajesh P. N. , Eagleman David M. , Sejnowski Terrence J.
Published: July 2002

When a flash is aligned with a moving object, subjects perceive the flash to lag behind the moving object. Two different models have been proposed to explain this “flash-lag” effect. In the motion extrapolation model, the visual system extrapolates the location of the moving object to counteract neural propagation delays, whereas in the latency difference model, it is hypothesized that moving objects are processed and perceived more quickly than flashed objects. However, recent psychophysical experiments suggest that neither of these interpretations is feasible (Eagleman & Sejnowski, 2000a, 2000b, 2000c), hypothesizing instead that the visual system uses data from the future of an event before committing to an interpretation. We formalize this idea in terms of the statistical framework of optimal smoothing and show that a model based on smoothing accounts for the shape of psychometric curves from a flash-lag experiment involving random reversals of motion direction. The smoothing model demonstrates how the visual system may enhance perceptual accuracy by relying not only on data from the past but also on data collected from the immediate future of an event.
An Information-Based Neural Approach to Constraint Satisfaction
Authors: Jönsson Henrik , Söderberg Bo
Published: July 2002

A novel artificial neural network approach to constraint satisfaction problems is presented. Based on information-theoretical considerations, it differs from a conventional mean-field approach in the form of the resulting free energy. The method, implemented as an annealing algorithm, is numerically explored on a testbed of K-SAT problems. The performance shows a dramatic improvement over that of a conventional mean-field approach and is comparable to that of a state-of-the-art dedicated heuristic (GSAT+walk). The real strength of the method, however, lies in its generality. With minor modifications, it is applicable to arbitrary types of discrete constraint satisfaction problems.
Spatial Orientation as a Component of Presence: Insights Gained from Nonterrestrial Environments
Authors: Lackner James R. , DiZio Paul
Published: July 2002

Spatial orientation is a substantial component of the sense of presence in real and virtual environments. Virtual environments have amazing versatility in terms of the possible modes of “entering” them, the positions occupants can take up within or in relation to them, and the ways virtual environments can be embedded within real ones. A virtual environment that differs too sharply in these respects from the normal terrestrial environment may challenge users' abilities to develop spatial orientation and a sense of presence within it, and to acquire spatial training that will transfer to real situations. We learned this fact while analyzing spatial orientation and presence in a variety of real experimental environments, including ones involving nonterrestrial gravitoinertial force backgrounds. One environment we investigated was “microgravity,” in which subjects can free float and be exposed to unique visual perspectives and patterns of touch and pressure cues on the body surface. A second was a rotating “artificial gravity” environment embedded within the larger context of a stationary laboratory complex. Our observations emphasize visual, vestibular, and somesthetic cues in construction of spatial representations of familiar environments. However, we have found that multiple levels of such representations exist, which interact with larger spatial constructs. The cognitive map of an environment depends on its represented embedding within associated environments and the directionality of modes of access between them. This dependency is reflected in the “wrong door phenomenon” that results when an individual enters a familiar environment from a nonfamiliar access position and becomes disoriented.
Learning and Building Together in an Immersive Virtual World
Authors: Roussos Maria , Johnson Andrew , Moher Thomas , Leigh Jason , Vasilakis Christina , Barnes Craig
Published: July 2002

This paper describes the design, evaluation, and lessons learned from a project involving the implementation of an immersive virtual environment for children called NICE (Narrative-based, Immersive, Constructionist/Collaborative Environments). The goal of the NICE project was to construct a testbed for the exploration of virtual reality as a learning medium within the context of the primary educational reform themes of the past three decades. With a focus on informal education and domains with social content, NICE embraces the constructivist approach to learning, collaboration, and narrative development, and is designed to utilize the strengths of virtual reality: a combination of immersion, telepresence, immediate visual feedback, and interactivity. Based on our experiences with a broad range of users, the paper discusses both the successes and limitations of NICE and concludes with recommendations for research directions in the application of immersive VR technologies to children's learning.
Structured Evaluation of Virtual Environments for Special-Needs Education
Authors: Neale H. R. , Brown D. J. , Cobb S. V. G. , Wilson J. R.
Published: July 2002

This paper describes the development of a structured approach to evaluate the experiential and communication virtual learning environments (VLEs) that were designed specifically for use in the education of children with severe learning difficulties at the Shepherd School in Nottingham. Constructivist learning theory was used as a basis for an evaluation framework and analysis method to evaluate the behavior of the participants as well as the quality of the design of three different VLEs. From an observational field study of student-teacher pairs using the VLEs, eighteen behavior categories were identified as relevant to five of seven constructivist principles (Jonassen, 1994). The analysis of student-teacher behavior was used to provide evidence for (or against) how the VLEs met the constructivist principles. Results of this structured evaluation indicate that the three VLEs meet the constructivist principles in very different ways. This paper concludes with recommendations for appropriate design modifications.
Recent Developments in the Evolution of Morphologies and Controllers for Physically Simulated Creatures
Authors: Taylor Tim , Massey Colm
Published: July 2002

Karl Sims' work [25, 26] on evolving body shapes and controllers for three-dimensional, physically simulated creatures generated wide interest on its publication in 1994. The purpose of this article is threefold: (a) to highlight a spate of recent work by a number of researchers in replicating, and in some cases extending, Sims' results using standard PCs (Sims' original work was done on a Connection Machine CM-5 parallel computer). In particular, a re-implementation of Sims' work by the authors will be described and discussed; (b) to illustrate how off-the-shelf physics engines can be used in this sort of work, and also to highlight some deficiencies of these engines and pitfalls when using them; and (c) to indicate how these recent studies stand in respect to Sims' original work.
THE INTERDICTION OF THE SPENDTHRIFT (AL-SAFĪH): A HUMAN RIGHTS DEBATE IN CLASSICAL FIQH
Authors: Arabi Oussama
Published: July 2002

A semantic equivalence between the Qur'ānic terms safīh and mubadhdhir underlies classical Islamic law's interdiction (hajr) of the spendthrift. The Qur'ān, however, is not explicit in endorsing the semantic equivalence of these two terms. To bridge this semantic gap, Muslim jurists exploited an opposition in Arabic usage between safah and rushd, extending the meaning of safīh from "one who lacks judgment" to "one who squanders his wealth". Subsequently, the safīh became the object of disagreement among the Hanafī master jurists: Abū Hanīfa placed a greater value on the sane adult's legal autonomy than on the preservation of his wealth; Abū Yūsuf and al-Shaybānī (together with Mālik, al-Shāfi ī and the Hanbalīs) held for the restriction of the adult prodigal's legal capacity. Ibn Hazm revived Abū Hanīfa's position by undertaking a lexicographical critique of the metaphorical extension of the meaning of safīh and by upholding the Muslim ideal of modest living.
Aristotle on Improving One's Character
Authors: Muzio Gianluca Di
Published: July 2002

Contrary to what most interpreters hold, in the Nicomachean Ethics Aristotle is not committed to the view that people of established vicious character could never become good. The present paper proves this result (1) by giving a better reading of 1114 a 12-21, a passage which has traditionally been taken to assert that unjust and self-indulgent people are doomed to a lifetime of vice; (2) by showing that when Aristotle refers to self-indulgent people as "incurable", he does not mean that they could never change, but only that they could not change as a result of external influences such as persuasion or punishment; (3) by proving that although Aristotle regards the desires of vicious people as determined by their character, there is room within Aristotelian moral psychology for the possibility that people of corrupt character become motivated to begin a process of moral reform.
Video Dog Star: William Wegman, Aesthetic Agency, and the Animal in Experimental Video Art
Authors: McHugh Susan
Published: July 2002

The canine photographs, videos, and photographic narratives of artist William Wegman frame questions of animal aesthetic agency. Over the past 30 years, Wegman's dog images shift in form and content in ways that reflect the artist's increasing anxiety over his control of the art-making process once he becomes identified, in his own words, as "the dog photographer". Wegman's dog images claim unique cultural prominence, appearing regularly in fine art museums as well as on broadcast television. But, as Wegman comes to use these images to document his own transition from dog photographer to dog breeder, these texts also reflect increasing restrictions on what I term the "pack aesthetics," or collaborative production of art and artistic agency, that distinguish some of the early pieces. Accounting for the correlations between multiple and mongrel dogs in Wegman's experimental video work and exclusively Weimaraner-breed dogs with human bodies in his recent work in large-format Polaroid photography, this article explores how Wegman's work with his "video dog star," his first Weimaraner dog Man Ray, troubles the erasure of the animal in contemporary conceptions of artistic authority.
IS THE BOOK OF ESTHER OLDER THAN HAS BEEN BELIEVED?
Authors: Larsson Gerhard
Published: July 2002

It has above been questioned for various reasons if it is possible - as proposed by Friedberg - to use the different designations of months in different biblical books as an indication of the age of the book in question.
Genomic Imprinting and the Cognitive Architecture Mediating Human Culture
Authors: Brown William Michael
Published: July 2002

Genomic imprinting may be implicated in the origin and maintenance of the cognitive architecture required for cultural transmission. Relatedness asymmetries are expected to lead to increases in the receptibility of matrilineally transmitted information. This may help explain why maternal genes contribute preferentially to the neocortex. That is, maternal genes could influence biases in the transmission and/or acquisition of information. This perspective is complementary to gene-culture coevolutionary approaches.
SOCIAL STATUS AND REPRODUCTIVE SUCCESS IN QUEENLESS ANT COLONIES
Authors: Trunzer  , Heinze  , Holldobler
Published: July 2002

Workers in queenless colonies of the ponerine ant Pachycondyla villosa establish linear or near-linear rank orders by antennation bouts and overt aggression. In these hierarchies, top-ranking individuals were reliably among the most productive egg-layers, but several lower ranking workers also laid considerable numbers of eggs. Though many of the subordinates' eggs were eaten by the-workers, we could show by multilocus DNA-fingerprinting that low-ranking individuals occasionally succeeded in producing adult males. However, the most dominant workers always had the highest reproductive success.
Isolation and localisation of an annexin gene (gp-nex) from the potato cyst nematode, Globodera pallida
Authors: Warry Andrew , Curtis Rosane , Porter Andrew , Fioretti Luca , Haydock Patrick
Published: July 2002

A full length cDNA clone was isolated by screening a mixed stage Globodera pallida expression library using the monospecific polyclonal antibody IACR-PC320. Sequence comparison indicated that the predicted 332 amino acid protein encoded by the cDNA was a member of the annexin gene family named gp-nex and very similar to annexins found in other nematode species. Annexins are calcium-dependent phospholipid binding proteins characterised by four repeated domains approximately 70 amino acids in length. The predicted amino acid sequence of the protein did not contain an N-terminal secretion signal peptide; however, the protein was shown to be present in excretory/secretory products from G. pallida second stage juveniles treated with the neurotransmitter 5 methoxy-N, N dimethyl tryptamine. Gp-nex encodes a protein of 35 kDa and was immunolocalised in the amphids, genital primordium and in the constraining muscles above and below the metacorpus pump chamber of G. pallida second stage juveniles. It is also present in eggs and adult females of the two species of the potato cyst nematodes.
Identification and ecological characterisation of three entomopathogenic nematode-bacterium complexes from Turkey
Authors: Susurluk Alper , Wyss Urs , Ehlers Ralf-Udo , Strauch Olaf , Stackebrandt Erko , Dix Ilona
Published: July 2002

Two heterorhabditid nematode strains (TUR-H1 and TUR-H2), and their bacterial symbionts isolated from soil samples taken at the campus of the Agriculture Faculty of the University of Ankara, Turkey, were identified by molecular methods and by cross-breeding with Heterorhabditis bacteriophora. The bacterial symbionts shared >99% similarity in the 16S rDNA sequence with Photorhabdus luminescens subsp. laumondii. Results of the restriction fragment length analysis of the ITS region assigned both nematode strains to the species H. bacteriophora. Cross-breeding confirmed the species designation for strain TUR-H2. Crosses of TUR-H1 with a hybrid strain of H. bacteriophora or with TUR-H2 resulted in infertile offspring. Both strains reproduced in monoxenic cultures of the symbionts P.luminescens isolated from H. bacteriophora and H. megidis and the resulting dauer juveniles retained cells of the bacteria. Reproduction on the symbionts isolated from H. indica failed. Infectivity at variable soil moisture and heat tolerance of the two heterorhabditid strains was compared with a Turkish isolate of Steinernema feltiae. Significantly more nematodes invaded the insect Galleria mellonella in a sandy soil assay at 10% water content than at lower values. A higher water content significantly reduced the invasion rate. Steinernema feltiae was better adapted to a temperature of 32°C than the heterorhabditid strains. Hardly any nematodes of all strains survived for longer than 4 h at 36°C.
Formation conditions of vesicle/fissure–filling smectites in Penghu basalts: a stable-isotope assessment
Authors: Yui Tzen-Fu , Chang Shyun-Sheng
Published: July 2002

Stable isotope and chemical compositions of vesicle- and fissure-filling smectites (i.e. montmorillonite and saponite) in Penghu subaerial basalts were analysed to establish their possible formation conditions. The results show that montmorillonites have higher Fe contents (as FeOtotal), as well as higher O-isotope and H-isotope compositions than saponites. These differences may largely reflect dissimilar formation conditions and/or fluid compositions. It is suggested that saponites probably precipitated from fluids dominated by meteoric groundwaters at 40–50°C, whereas montmorillonites were probably formed at 20–40°C from mixtures of groundwaters and seawater. Considering all the possible uncertainties, the above estimated temperature conditions are suggested as reasonable lower limits.

It is established that the associated calcite is not in O-isotope equilibrium with the montmorillonite. The calcite might have been formed in environments with ambient fluid dominated by meteoric groundwaters at temperatures lower than those for montmorillonite.
Surface modification of bentonites: I. Betaine montmorillonites and their rheological and colloidal properties
Authors: Schmidt C. U. , Lagaly G.
Published: July 2002

Montmorillonite was modified by replacing the exchangeable cations with betaines

(CH3)3N+ - (CH2)n - COO-M+ (n = 3, 5, 7, 10)

The betaine derivatives delaminated in water and formed a colloidal dispersion. Air-drying of this material yielded hard pieces which were difficult to redisperse. The dried material became redispersible in water when the Na ions (counterions to the carboxyl groups) were replaced by Li ions. Colloidal dispersions of this material were more stable against salts than Li+- or Na+ - montmorillonite. Extremely high LiCl concentrations (>1 mol/l) were needed to coagulate the betaine derivatives (n>5) in the presence of diphosphate. The increased salt stability resulted from lyospheres around the silicate layers or thin packets of them which reduced the van der Waals attraction. Addition of organic solvents destabilized the dispersion by compressing the diffuse ionic layer (DLVO theory). The delaminated particles then aggregated to small flocs which settled very slowly. Neither band-type structures nor cardhouses were formed at conditions comparable to network formation and stiffening of Li- and Na-montmorillonite dispersions. Rheological measurements revealed the liquefying action of the betaines. Dispersions of butyrobetaine montmorillonite (15 g solid/l) revealed a relative viscosity (related to the dispersion medium water) ηrel ≈ 2. The longer chain derivatives showed a value slightly >1 whereas Li+-montmorillonite had ηrel = 8. Yield values were not formed at pH ≈ 7. Only at acidic conditions did the butyrobetaine montmorillonite dispersion showed a small yield value (<200 mPa).
Dienerite – a mystification
Authors: Bayliss P.
Published: July 2002

The mineral name dienerite should be allowed to slip into obsolescence. Dienerite AsNi3–xis probably nickelskutterudite As3–xNi caused by a typographical error in the chemical analysis.
Actin reorganization and proplatelet formation in murine megakaryocytes: the role of protein kinase Cα
Authors: Rojnuckarin Ponlapat , Kaushansky Kenneth
Published: July 2002

With the recent cloning and characterization of thrombopoietin, appreciation of the molecular events surrounding megakaryocyte (MK) development is growing. However, the final stages of platelet formation are less well understood. Platelet production occurs after the formation of MK proplatelet processes. In a study to explore the molecular mechanisms underlying this process, mature MKs isolated from suspension murine bone marrow cell cultures were induced to form proplatelets by exposure to plasma, and the role of various cell-signaling pathways was assessed. The results showed that (1) bis-indolylmaleimide I, which blocks protein kinase C (PKC) activation; (2) down-modulation of conventional or novel classes of PKC by phorbol myristate acetate; and (3) ribozymes specific for PKCα each inhibited proplatelet formation. Inhibition of several MAP kinases, PI3 kinase, or protein kinase A failed to affect MK proplatelet formation. To gain further insights into the function of PKCα in proplatelet formation, its subcellular localization was investigated. In cultures containing active proplatelet formation, cytoplasmic polymerized actin was highly aggregated, its subcellular distribution was reorganized, and PKCα colocalized with the cellular actin aggregates. A number of MK manipulations, including blockade of integrin signaling with a disintegrin or inhibition of actin polymerization with cytochalasin D, interrupted actin reorganization, PKC relocalization, and proplatelet formation. These findings suggest an important role for PKCα in proplatelet development and suggest that it acts by altering actin dynamics in proplatelet-forming MKs. Identification of the upstream and downstream pathways involved in proplatelet formation should provide greater insights into thrombopoiesis, potentially allowing pharmacologic manipulation of the process.