bluuebunny/crossref_metadata_2025 huggingface dataset:
On taxonomic reasoning in conceptual design
Authors: Bergamaschi Sonia , Sartori Claudio
Published: July 2002

Taxonomic reasoning is a typical task performed by many AI knowledge representation systems. In this paper, the effectiveness of taxonomic reasoning techniques as an active support to knowledge acquisition and conceptual schema design is shown. The idea developed is that by extending conceptual models with
defined concepts
and giving them rigorous logic semantics, it is possible to infer
isa
relationships between concepts on the basis of their descriptions. From a theoretical point of view, this approach makes it possible to give a formal definition for
consistency
and
minimality
of a conceptual schema. From a pragmatic point of view it is possible to develop an active environment that allows automatic
classification
of a new concept in the right position of a given taxonomy, ensuring the consistency and minimality of a conceptual schema. A formalism that includes the data semantics of models giving prominence to type constructors (E/R, TAXIS, GALILEO) and algorithms for taxonomic inferences are presented: their soundness, completeness, and tractability properties are proved. Finally, an extended formalism and taxonomic inference algorithms for models giving prominence to attributes (FDM, IFO) are given.
Computing tensor product decompositions
Authors: Snow Dennis M.
Published: July 2002

An algorithm is presented for computing the decomposition of a tensor product of two irreducible representations of a semisimple complex Lie group into its irreducible components. The algorithm uses a known formula which expresses the multiplicities of the highest weight vectors in the decomposition as an alternating sum indexed by the Weyl group. This sum is accomplished with minimal memory requirements using techniques developed previously by the author for efficiently computing Weyl group orbits. Examples are given for each of the exceptional Lie groups.
Serverless network file systems
Authors: Anderson Thomas E. , Dahlin Michael D. , Neefe Jeanna M. , Patterson David A. , Roselli Drew S. , Wang Randolph Y.
Published: July 2002

We propose a new paradigm for network file system design:serverless network file systems. While traditional network file systems rely on a central server machine, a serverless system utilizes workstations cooperating as peers to provide all file system services. Any machine in the system can store, cache, or control any block of data. Our approach uses this location independence, in combination with fast local area networks, to provide better performance and scalability than traditional file systems. Furthermore, because any machine in the system can assume the responsibilities of a failed component, our serverless design also provides high availability via redundatn data storage. To demonstrate our approach, we have implemented a prototype serverless network file system called xFS. Preliminary performance measurements suggest that our architecture achieves its goal of scalability. For instance, in a 32-node xFS system with 32 active clients, each client receives nearly as much read or write throughput as it would see if it were the only active client.
Compositional refinement of interactive systems
Authors: Broy Manfred
Published: July 2002

We introduce a method to describe systems and their components by functional specification techniques. We define notions of interface and interaction refinement for interactive systems and their components. These notions of refinement allow us to change both the syntactic (the number of channels and sorts of messages at the channels) and the semantic interface (causality flow between messages and interaction granularity) of an interactive system component. We prove that these notions of refinement are compositional with respect to sequential and parallel composition of system components, communication feedback and recursive declarations of system components. According to these proofs, refinements of networks can be accomplished in a modular way by refining their compponents. We generalize the notions of refinement to refining contexts. Finally, full abstraction for specifications is defined, and compositionality with respect to this abstraction is shown, too.
The 1985-1986 Taulbee survey
Authors: Gries David
Published: July 2002

The Computing Research Board's latest survey on the production and employment of Ph.D.'s and faculty in computer science and engineering depicts a young, optimistic discipline where supply may not always meet demand.
Transactions and consistency in distributed database systems
Authors: Traiger Irving L. , Gray Jim , Galtieri Cesare A. , Lindsay Bruce G.
Published: July 2002

The concepts of transaction and of data consistency are defined for a distributed system. The cases of partitioned data, where fragments of a file are stored at multiple nodes, and replicated data, where a file is replicated at several nodes, are discussed. It is argued that the distribution and replication of data should be transparent to the programs which use the data. That is, the programming interface should provide location transparency, replica transparency, concurrency transparency, and failure transparency. Techniques for providing such transparencies are abstracted and discussed.

By extending the notions of system schedule and system clock to handle multiple nodes, it is shown that a distributed system can be modeled as a single sequential execution sequence. This model is then used to discuss simple techniques for implementing the various forms of transparency.
A unifying model of physical databases
Authors: Batory D. S. , Gotlieb C. C.
Published: July 2002

A unifying model for the study of database performance is proposed. Applications of the model are shown to relate and extend important work concerning batched searching, transposed files, index selection, dynamic hash-based files, generalized access path structures, differential files, network databases, and multifile query processing.
Production and Stabilization of Real-Time Task Schedules
Authors: Manacher G. K.
Published: July 2002

A model for multiprocessor control is considered in which jobs are broken into various pieces, called
tasks
. Tasks are executed by single processing units. In this paper the structure controlling the assignment of tasks to processors is the
task list,
which orders all tasks according to servicing priority. When a processors becomes free, it simply picks up the highest priority task that is executable at that moment.

The job and its component tasks are imagined to be interacting with an environment consisting of a set of rigid
timing constraints
. Such constraints are of two types, called
start-times
and
deadlines
. The interaction is specified by requiring that certain distinguished tasks conform directly to one or more of these constraints. Tasks conforming to a start-time cannot begin until the start-time has passed, and tasks conforming to a deadline cannot proceed beyond the deadline. In our model, all tasks have known
maximum
run-times, but in any particular job execution, task run-times are unknown.

It is shown that despite the simplicity of this control scheme some peculiar phenomena result. Most of these phenomena were first noticed by P. Richards in 1960. A simulation study (Appendix I) reveals that they may be very common in practice. In the present paper and a companion paper by R. L. Graham [
Bell Syst. Tech. J. 45
(1966), 1563-1581] a coherent theory of task-list control is developed, in which the nature of these peculiarities is brought under systematic study. A number of potentially useful results are derived.
Transforming LR(
k
) Grammars to LR(1), SLR(1), and (1,1) Bounded Right-Context Grammars
Authors: Mickunas M. D. , Lancaster R. L. , Schneider V. B.
Published: July 2002

A method is presented for directly transforming an arbitrary LR(
k
) grammar to an equivalent LR(1) grammar. It is further shown that the method transforms an arbitrary prefix-free LR(
k
) grammar to an equivalent LR(0) grammar. It is argued that the method is efficient and offers some advantages over traditional “look-ahead” parsing methods. Finally, it is demonstrated that the method can be used to transform an LR(1) grammar to an equivalent SLR(1) grammar, which in turn can be easily transformed to an equivalent (1, 1) bounded right-context grammar.
The partial metrics system: modeling the stepwise refinement process using partial metrics
Authors: Reynolds Robert G.
Published: July 2002

The Partial Metrics System design is explained, with an emphasis on the refinement process. A model, with its three phases, shows that the pseudocode refinement process can be monitored in partial metric terms.
Blocked algorithms and software for reduction of a regular matrix pair to generalized Schur form
Authors: Dackland Krister , Kågström Bo
Published: July 2002

A two-stage blocked algorithm for reduction of a regular matrix pair (
A , B
) to upper Hessenberg-triangular form is presented. In stage 1 (
A, B
is reduced to block upper Hessenberg-triangular form using mainly level 3 (matrix-matrix) operations that permit data reuse in the higher levels of a memory hierarchy. In the second stage all but one of the
r
subdiagonals of the block Hessenberg
A
-part are set to zero using Givens rotations. The algorithm proceeds in a sequence of supersweeps, each reducing
m
columns. The updates with respect to row and column rotations are organized to reference consecutive columns of
A
and
B
. To further improve the data locality, all rotations produced in a supersweep are stored to enable a left-looking reference pattern, i.e., all updates are delayed until they are required for the continuation of the supersweep. Moreover, we present a blocked variant of the single-diagonal double-shift
QZ
method for computing the generalized Schur form of (
A, B
in upper Hessenberg-triangular form. The blocking for improved data locality is done similarly, now by restructuring the reference pattern of the updates associated with the bulge chasing in the
QZ
iteration. Timing results show that our new blocked variants outperform the current LAPACK routines, including drivers for the generalized eigenvalue problem, by a factor 2-5 for sufficiently large problems.
A note on sub-expression ordering in the execution of arithmetic expressions
Authors: Denning Peter J. , Graham G. Scott
Published: July 2002

A counterexample to the supposed optimality of an algorithm for generating schedules for trees of tasks with unequal execution times is presented. A comparison with the “critical path” heuristic is discussed.
The cyclical majority problem
Authors: Pomeranz John E. , Weil Roman L.
Published: July 2002

The problem of the cyclical majority is presented and some new, simulated results for 3, 4, 5, … , 40 issues and 3, 5, 7, … , 37 judges are reported.
On the design of a learning crawler for topical resource discovery
Authors: Aggarwal Charu C. , Al-Garawi Fatima , Yu Philip S.
Published: July 2002

In recent years, the World Wide Web has shown enormous growth in size. Vast repositories of information are available on practically every possible topic. In such cases, it is valuable to perform topical resource discovery effectively. Consequently, several new ideas have been proposed in recent years; among them a key technique is focused crawling which is able to crawl particular topical portions of the World Wide Web quickly, without having to explore all web pages. In this paper, we propose the novel concept of intelligent crawling which actually
learns
characteristics of the linkage structure of the World Wide Web while performing the crawling. Specifically, the intelligent crawler uses the inlinking web page content, candidate URL structure, or other behaviors of the inlinking web pages or siblings in order to estimate the probability that a candidate is useful for a given crawl. This is a much more general framework than the focused crawling technique which is based on a pre-defined understanding of the topical structure of the web. The techniques discussed in this paper are applicable for crawling web pages which satisfy arbitrary user-defined predicates such as topical queries, keyword queries, or any combinations of the above. Unlike focused crawling, it is not necessary to provide representative topical examples, since the crawler can learn its way into the appropriate topic. We refer to this technique as
intelligent crawling
because of its adaptive nature in adjusting to the web page linkage structure. We discuss how to intelligently select features which are most useful for a given crawl. The learning crawler is capable of reusing the knowledge gained in a given crawl in order to provide more efficient crawling for closely related predicates.
High-speed implementations of rule-based systems
Authors: Gupta A. , Forgy C. , Newell A.
Published: July 2002

Rule-based systems are widely used in artificial intelligence for modeling intelligent behavior and building expert systems. Most rule-based programs, however, are extremely computation intensive and run quite slowly. The slow speed of execution has prohibited the use of rule-based systems in domains requiring high performance and real-time response. In this paper we explore various methods for speeding up the execution of rule-based systems. In particular, we examine the role of parallelism in the high-speed execution of rule-based systems and study the architectural issues in the design of computers for rule-based systems. Our results show that contrary to initial expectations, the speed-up that can be obtained from parallelism is quite limited, only about tenfold. The reasons for the small speed-up are: (1) the small number of rules relevant to each change to data memory; (2) the large variation in the processing requirements of relevant rules; and (3) the small number of changes made to data memory between synchronization steps. Furthermore, we observe that to obtain this limited factor of tenfold speed-up, it is necessary to exploit parallelism at a very fine granularity. We propose that a suitable architecture to exploit such fine-grain parallelism is a shared-memory multiprocessor with 32-64 processors. Using such a multiprocessor, it is possible to obtain execution speeds of about 3800 rule-firings/set. This speed is significantly higher than that obtained by other proposed parallel implementations of rule-based systems.
The Arts of Government in Early Mesoamerica
Authors: Clark J. E.
Published: July 2002

This review addresses issues of governmentality for Mesoamerica's earliest kingdoms. About 3200 years ago the Olmecs instituted stratified society based upon sacred kingship. Supervision of public works projects, the creation and deployment of monumental art, and control of ritual and ideology were the kings' principal means of governance within their kingdoms. Evidence for Olmec governance outside their region is equivocal. Olmecs may have conquered the societies of the Mazatan region, but they interacted with societies in the Mexican Highlands on a less coercive and more equitable basis.
GENETICS OF MODERN HUMAN ORIGINS AND DIVERSITY
Authors: Relethford John H.
Published: July 2002

▪ Abstract  A major and continuing debate in anthropology concerns the question of whether modern Homo sapiens emerged as a separate species roughly 200,000 years ago in Africa (recent African origin model) or as the consequence of evolution within a polytypic species spread across several regions of the Old World (multiregional model). Genetic data have been used to address this debate, focusing on the analysis of gene trees, genetic diversity within populations, and genetic differences between populations. Although the genetic data do provide support for the recent African origin model, they also are compatible with the multiregional model. The genetic evidence provides little direct inference regarding phylogeny, but it can tell us a great deal about ancient demography. Currently, neither model of modern human origins is unequivocally supported to the exclusion of the other.
Australopithecus to Homo: Transformations in Body and Mind
Authors: McHenry Henry M. , Coffing Katherine
Published: July 2002

▪ Abstract  Significant changes occurred in human evolution between 2.5 and 1.8 million years ago. Stone tools first appeared, brains expanded, bodies enlarged, sexual dimorphism in body size decreased, limb proportions changed, cheek teeth reduced in size, and crania began to share more unique features with later Homo. Although the two earliest species of Homo, H. habilis and H. rudolfensis, retained many primitive features in common with australopithecine species, they both shared key unique features with later species of Homo. Two of the most conspicuous shared derived characters were the sizes of the brain and masticatory apparatus relative to body weight. Despite the shared derived characters of H. habilis and H. rudolfensis, one unexpected complication in the transition from australopithecine to Homo was that the postcranial anatomy of H. habilis retained many australopithecine characteristics. H. rudolfensis, however, seems to have had a more human-like body plan, similar to later species of Homo. H. rudolfensis may therefore represent a link between Australopithecus and Homo.
Ribozyme Structures and Mechanisms
Authors: Doherty Elizabeth A. , Doudna Jennifer A.
Published: July 2002

▪ Abstract  The past few years have seen exciting advances in understanding the structure and function of catalytic RNA. Crystal structures of several ribozymes have provided detailed insight into the folds of RNA molecules. Models of other biologically important RNAs have been constructed based on structural, phylogenetic, and biochemical data. However, many questions regarding the catalytic mechanisms of ribozymes remain. This review compares the structures and possible catalytic mechanisms of four small self-cleaving RNAs: the hammerhead, hairpin, hepatitis delta virus, and in vitro–selected lead-dependent ribozymes. The organization of these small catalysts is contrasted to that of larger ribozymes, such as the group I intron.
NOx EMISSIONS FROM SOIL: Implications for Air Quality Modeling in Agricultural Regions
Authors: Hall Sharon J. , Matson Pamela A. , Roth Philip M.
Published: July 2002

▪ Abstract  Attaining the ambient standard for tropospheric ozone has been difficult in many metropolitan areas, despite efforts to reduce anthropogenic sources of the ozone precursors, including the nitrogen oxides (NOx). Until recently, NOx emissions from biogenic sources in soils were not considered in simulations of air quality and emissions reductions scenarios, yet they may be significant, especially in agricultural regions where nitrogen fertilizers are applied. Soil NOx is produced primarily by microbial processes; production and emissions from soils are controlled by a suite of environmental variables, including inorganic nitrogen availability, water-filled pore space, and soil temperature. Agricultural management practices such as fertilization and irrigation affect these environmental variables and thus have the potential to dramatically alter soil NOx emissions. Although current models incorporate some of these variables, accurate regional estimation of soil NOx emissions requires modeling approaches that explicitly incorporate the spatial and temporal patterns of management practices, especially fertilization, as well as other environmental controlling variables such as water-filled pore space and soil temperature.
INSECT ACID-BASE PHYSIOLOGY
Authors: Harrison Jon F.
Published: July 2002

▪ Abstract  Acid-base status influences many aspects of insect biology, including insect distributions in aquatic systems, insect-plant and insect-pathogen interactions, membrane transport phenomena, and the mode of action of pesticides. Acid-base status in the hemolymph and gut lumen of insects is generally well regulated but varies somewhat within individuals owing to effects of temperature, activity, discontinuous ventilation, and diet. The pH of the midgut lumen varies with the phylogeny and feeding ecology. Insect fluids have buffer values similar to those of vertebrates. The respiratory system participates in acid-base homeostasis primarily by regulating the internal carbon dioxide (partial) pressure via changes in spiracular opening and convective ventilation. The epithelia of the renal system and gut participate in hemolymph acid-base regulation by varying acid-base transport in response to organismal acid-base status. Evidence to date suggests that the dominant mechanisms for control of renal acid-base excretion involve hormonal regulation of H+-V-ATPase activity.
Genetic Perspectives on Human Origins and Differentiation
Authors: Harpending Henry , Rogers Alan
Published: July 2002

This is a review of genetic evidence about the ancient demography of the ancestors of our species and about the genesis of worldwide human diversity. The issue of whether or not a population size bottleneck occurred among our ancestors is under debate among geneticists as well as among anthropologists. The bottleneck, if it occurred, would confirm the Garden of Eden (GOE) model of the origin of modern humans. The competing model, multiregional evolution (MRE), posits that the number of human ancestors has been large, occupying much of the temperate Old World for the last two million years. While several classes of genetic marker seem to contain a strong signal of demographic recovery from a small number of ancestors, other nuclear loci show no such signal. The pattern at these loci is compatible with the existence of widespread balancing selection in humans. The study of human diversity at (putatively) neutral genetic marker loci has been hampered since the beginning by ascertainment bias since they were discovered in Europeans. The high levels of polymorphism at microsatellite loci means that they are free of this bias. Microsatellites exhibit a clear almost linear diversity gradient away from Africa, so that New World populations are approximately 15% less diverse than African populations. This pattern is not compatible with a model of a single large population expansion and colonization of most of the Earth by our ancestors but suggests, instead, gradual loss of diversity in successive colonization bottlenecks as our species grew and spread.
THE GENETIC DEFECT IN ATAXIA-TELANGIECTASIA
Authors: Lavin Martin F. , Shiloh Yosef
Published: July 2002

▪ Abstract  The autosomal recessive human disorder ataxia-telangiectasia (A-T) was first described as a separate disease entity 40 years ago. It is a multisystem disease characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia, radiosensitivity, predisposition to lymphoid malignancies and immunodeficiency, with defects in both cellular and humoral immunity. The pleiotropic nature of the clinical and cellular phenotype suggests that the gene product involved is important in maintaining stability of the genome but also plays a more general role in signal transduction. The chromosomal instability and radiosensitivity so characteristic of this disease appear to be related to defective activation of cell cycle checkpoints. Greater insight into the nature of the defect in A-T has been provided by the recent identification, by positional cloning, of the responsible gene, ATM. The ATM gene is related to a family of genes involved in cellular responses to DNA damage and/or cell cycle control. These genes encode large proteins containing a phosphatidylinositol 3-kinase domain, some of which have protein kinase activity. The mutations causing A-T completely inactivate or eliminate the ATM protein. This protein has been detected and localized to different subcellular compartments.
DIFFERENTIAL DIAGNOSIS AND MANAGEMENT OF CUSHING'S SYNDROME
Authors: Tsigos, M.D., Ph.D Constantine , Chrousos, M.D George P.
Published: July 2002

▪ Abstract  The diagnosis of endogenous Cushing's syndrome requires demonstration of an increased cortisol secretion rate, best achieved by urinary free cortisol excretion determinations. In borderline or confusing cases, loss of diurnal cortisol rhythmicity, a combined dexamethasone/corticotropin releasing hormone (CRH) test, or close monitoring of the patient for a few months will be helpful in ruling out pseudo- Cushing's. Primary adrenal Cushing's syndrome can be ruled out on the basis of a normal or elevated basal and/or CRH-stimulated plasma adrenocorticotropin (ACTH) and a negative adrenal computed tomography. ACTH-dependent Cushing's syndrome can then be differentiated on the basis of a CRH test and imaging procedures. A discrete pituitary lesion on magnetic resonance imaging and a standard CRH test with results consistent with such a lesion are sufficient to proceed to transsphenoidal surgery. If no discrete pituitary lesion is present, or if the CRH test is equivocal, bilateral simultaneous inferior petrosal sinus sampling with CRH administration is necessary to distinguish between a pituitary and an ectopic source. Surgery is the treatment of choice for all types of Cushing's syndrome. In the few cases in which transsphenoidal surgery fails or the disease recurs, repeat transsphenoidal surgery, or radiation therapy in association with mitotane treatment, is a reasonable alternative. Bilateral adrenalectomy effectively cures hypercortisolism if resection of the ACTH-secreting tumor is unsuccessful and radiation/medical therapy fails.
Intercellular Signaling During Fruiting-Body Development of Myxococcus xanthus
Authors: Shimkets Lawrence J.
Published: July 2002

▪ Abstract  The myxobacterium Myxococcus xanthus has a life cycle that is dominated by social behavior. During vegetative growth, cells prey on other bacteria in large groups that have been likened to wolf packs. When faced with starvation, cells form a macroscopic fruiting body containing thousands of spores. The social systems that guide fruiting body development have been examined through the isolation of conditional developmental mutants that can be stimulated to develop in the presence of wild-type cells. Extracellular complementation is due to the transfer of soluble and cell contact-dependent intercellular signals. This review describes the current state of knowledge concerning cell-cell signaling during development.
VERTEBRATE NEURAL INDUCTION
Authors: Hemmati-Brivanlou A. , Melton D.
Published: July 2002

▪ Abstract  During early vertebrate development, the cells of the ectoderm choose between two possible fates: neural and epidermal. The process of neural induction was discovered nearly 70 years ago in vertebrates, and molecular analyses in recent years using Xenopus laevis embryos have identified several secreted factors with direct neural-inducing ability. There is considerable evidence that the mechanism of neuralization by these inducing factors is under inhibitory control and involves derepression. This review focuses on factors involved in the specification of neural fate within the frame of the default model of neural induction.
ION CHANNELS IN VASCULAR ENDOTHELIUM
Authors: Nilius Bernd , Viana Félix , Droogmans Guy
Published: July 2002

▪ Abstract  The functional impact of ion channels in vascular endothelial cells (ECs) is still a matter of controversy. This review describes different types of ion channels in ECs and their role in electrogenesis, Ca2+ signaling, vessel permeability, cell-cell communication, mechano-sensor functions, and pH and volume regulation. One major function of ion channels in ECs is the control of Ca2+ influx either by a direct modulation of the Ca2+ influx pathway or by indirect modulation of K+ and Cl− channels, thereby clamping the membrane at a sufficiently negative potential to provide the necessary driving force for a sustained Ca2+ influx. We discuss various mechanisms of Ca2+ influx stimulation: those that activate nonselective, Ca2+-permeable cation channels or those that activate Ca2+-selective channels, exclusively or partially operated by the filling state of intracellular Ca2+ stores. We also describe the role of various Ca2+- and shear stress-activated K+ channels and different types of Cl− channels for the regulation of the membrane potential.
Cardiac Ion Channels
Authors: Roden Dan M. , Balser Jeffrey R. , George Jr Alfred L. , Anderson Mark E.
Published: July 2002

▪ Abstract  The normal electrophysiologic behavior of the heart is determined by ordered propagation of excitatory stimuli that result in rapid depolarization and slow repolarization, thereby generating action potentials in individual myocytes. Abnormalities of impulse generation, propagation, or the duration and configuration of individual cardiac action potentials form the basis of disorders of cardiac rhythm, a continuing major public health problem for which available drugs are incompletetly effective and often dangerous. The integrated activity of specific ionic currents generates action potentials, and the genes whose expression results in the molecular components underlying individual ion currents in heart have been cloned. This review discusses these new tools and how their application to the problem of arrhythmias is generating new mechanistic insights to identify patients at risk for this condition and developing improved antiarrhythmic therapies.
Noise in Integrate-and-Fire Neurons: From Stochastic Input to Escape Rates
Authors: Plesser Hans E. , Gerstner Wulfram
Published: July 2002

We analyze the effect of noise in integrate-and-fire neurons driven by time-dependent input and compare the diffusion approximation for the membrane potential to escape noise. It is shown that for time-dependent subthreshold input, diffusive noise can be replaced by escape noise with a hazard function that has a gaussian dependence on the distance between the (noise-free) membrane voltage and threshold. The approximation is improved if we add to the hazard function a probability current proportional to the derivative of the voltage. Stochastic resonance in response to periodic input occurs in both noise models and exhibits similar characteristics.
Computational Design and Nonlinear Dynamics of a Recurrent Network Model of the Primary Visual Cortex*
Authors: Li Zhaoping
Published: July 2002

Recurrent interactions in the primary visual cortex make its output a complex nonlinear transform of its input. This transform serves preattentive visual segmentation, that is, autonomously processing visual inputs to give outputs that selectively emphasize certain features for segmentation. An analytical understanding of the nonlinear dynamics of the recurrent neural circuit is essential to harness its computational power. We derive requirements on the neural architecture, components, and connection weights of a biologically plausible model of the cortex such that region segmentation, figure-ground segregation, and contour enhancement can be achieved simultaneously. In addition, we analyze the conditions governing neural oscillations, illusory contours, and the absence of visual hallucinations. Many of our analytical techniques can be applied to other recurrent networks with translation-invariant neural and connection structures.
Statistically Efficient Estimation Using Population Coding
Authors: Pouget Alexandre , Zhang Kechen , Deneve Sophie , Latham Peter E.
Published: July 2002

Coarse codes are widely used throughout the brain to encode sensory and motor variables. Methods designed to interpret these codes, such as population vector analysis, are either inefficient (the variance of the estimate is much larger than the smallest possible variance) or biologically implausible, like maximum likelihood. Moreover, these methods attempt to compute a scalar or vector estimate of the encoded variable. Neurons are faced with a similar estimation problem. They must read out the responses of the presynaptic neurons, but, by contrast, they typically encode the variable with a further population code rather than as a scalar. We show how a nonlinear recurrent network can be used to perform estimation in a near-optimal way while keeping the estimate in a coarse code format. This work suggests that lateral connections in the cortex may be involved in cleaning up uncorrelated noise among neurons representing similar variables.
Nomadmedia, On Critical Art Ensemble
Authors: Schneider Rebecca
Published: July 2002

The Critical Acts Ensemble, CAE for short, is a tightly knit group of artists exploring intersection between art, technology, critical theory, and political activism. We have given CAE a big chunk of space to present and explain their work. Added to that is a critical essay by TDR Contributing Editor Rebecca Schneider.
Living Newspaper: Theatre and Therapy
Authors: Casson John W.
Published: July 2002

Living Newspapers—a hallmark of the Federal Theatre Project of the 1930s—were foretold in 1915 by the Italian futurists, brought into existence in 1919 in the Soviet Union, further developed in Vienna in the 1920s by the founder of psychodrama, Jacob Moreno, played in India in the 1960s and after, and are used as therapy today.
Artificial Chemistries—A Review
Authors: Dittrich Peter , Ziegler Jens , Banzhaf Wolfgang
Published: July 2002

This article reviews the growing body of scientific work in artificial chemistry. First, common motivations and fundamental concepts are introduced. Second, current research activities are discussed along three application dimensions: modeling, information processing, and optimization. Finally, common phenomena among the different systems are summarized. It is argued here that artificial chemistries are “the right stuff” for the study of prebiotic and biochemical evolution, and they provide a productive framework for questions regarding the origin and evolution of organizations in general. Furthermore, artificial chemistries have a broad application range of practical problems, as shown in this review.
New Environmental Architectures and the Search for Effectiveness
Authors: Newell Peter
Published: July 2002

The starting point for a discussion of reform of the global environmental machinery has to be an inquiry into the causes of ineffectiveness of current arrangements. This article argues first that many of the criticisms made of the existing architecture are misplaced while ignoring other key faults. Second, argues that the means of operationalizing an alternative World Environment Organization (WEO) are problematic and may exacerbate existing problems, particularly for developing countries. The article focuses here more on the notion that a WEO should pursue the internalization of environmental externalities. It argues that while this goal is worth pursuing, proposals for a deal-brokering body are unlikely to make much progress in delivering it because of misplaced assumptions about both the existing political order and about the ability of a WEO to remedy current weaknesses.
Cultural, Gender, and Individual Differences in Perceptual and Semantic Structures of Basic Colors in Chinese and English
Authors: Moore Carmella , Romney A. Kimball , Hsia Ti-Lien
Published: July 2002

In this paper we examine the judged similarity among the eight basic focal colors, and their names, among female and male Chinese (n = 68) and English (n = 52) speaking respondents. The major findings are: (1) all respondents share approximately sixty percent of their knowledge of the judged similarity structures of both semantic and perceptual tasks, (2) there are genuine individual differences among respondents that account for about fourteen percent of their knowledge on average, (3) there are small but statistically significant gender differences that come to about three percent on average, (4) there are small but statistically significant differences between Chinese and English respondents of about one-and-a-half percent, (5) there are differences in the semantic structure of the names of colors as compared to the judgments of the color samples that amounts to about five percent, and (6) there is about a three percent difference in the paired comparison task and the triads task. The results place strong constraints on theories relating to individual differences, linguistic relativity, and the relation of perceptual and semantic structures for colors.
The Use of Modifying Terms in the Naming and Categorization of Color Appearances in Vietnamese and English
Authors: Alvarado Nancy , Jameson Kimberly
Published: July 2002

Cross-cultural studies of color naming show that basic terms are universally the most frequently used to name colors. However, such basic color terms are always used in the context of larger linguistic systems when specific properties of color experience are described. To investigate naturalistic naming behaviors, we examined the use of modifiers in English and Vietnamese color naming using an unconstrained naming task (Jameson & Alvarado, in press). Monolingual and bilingual subjects named a representative set of 110 color stimuli sampled from a commonly used color-order stimulus space. Results revealed greater reliance upon polylexemic naming among monolingual Vietnamese speakers and greater use of monolexemic basic hue terms and secondary terms (object glosses) among monolingual English speakers. Systematic differences across these language groups imply that widely used monolexemic naming methods may differentially impact color-naming findings in cross-cultural investigations of color cognition.
Immunoglobulin heavy-chain gene rearrangement in adult acute lymphoblastic leukemia reveals preferential usage of JH-proximal variable gene segments
Authors: Mortuza Forida Y. , Moreira Ilidia M. , Papaioannou Maria , Gameiro Paula , Coyle Luke A. , Gricks Clair S. , Amlot Peter , Prentice Hugh Grant , Madrigal Alejandro , Hoffbrand Alan Victor , Foroni Letizia
Published: July 2002

The aim of this study was to characterize individual-segment and overall patterns of VH gene usage in adult B-lineage acute lymphoblastic leukemia (ALL). Theoretical values of VH segment usage were calculated with the assumption that all VH segments capable of undergoing rearrangement have an equal probability of selection for recombination. Leukemic clones from 127 patients with adult B-lineage acute leukemias were studied by fingerprinting by means of primers for the framework 1 and joining segments. Clones from early preimmune B cells (245 alleles identified) show a predominance of VH6 family rearrangements and, consequently, do not conform to this hypothesis. However, profiles of VH gene family usage in mature B cells, as investigated in peripheral blood (6 samples), B-cell lymphomas (36 clones) and chronic lymphocytic leukemia (56 clones), are in agreement with this theoretical profile. Sequence analyses of 64 VH clones in adult ALL revealed that the rate of VH usage is proportional to the proximity of the VH gene to the JH locus and that the relationship can be mathematically defined. Except for VH6, no other VH gene is excessively used in adult ALL. VH pseudogenes are rarely used (n = 2), which implies the existence of early mechanisms in the pathway to B-cell maturation to reduce wasteful VH-(DH)-JHrecombination. Finally, similar to early immunoglobulin-H rearrangement patterns in the mouse, B cells of ALL derive from a pool of cells more immature than the cells in chronic lymphoid B-cell malignancies.
Long-lived polyclonal B-cell lines derived from midgestation mouse embryo lymphohematopoietic progenitors reconstitute adult immunodeficient mice
Authors: Martı́nez-M. José A. , Minguet Susana , Gonzalo Pilar , Soro Pilar G. , de Andrés Belén , Ízcue Ana , Marcos Miguel A. R. , Gaspar Marı́a-Luisa
Published: July 2002

Lymphohematopoietic progenitors derived from midgestation mouse embryos were established in long-term cultures with stromal cell monolayers and interleukin 7 (IL-7), giving rise to B-lineage cell lines. The initial emergence and in vitro establishment of these early embryo cell lines were highly sensitive to IL-7–mediated signals, in comparison to cell lines similarly obtained using precursors from late fetal liver (> 13 days postcoitum) and adult bone marrow. The early embryo-derived progenitors spontaneously differentiated in vitro to CD19+IgM+ immature B cells in the presence of optimal concentrations of IL-7, in contrast to those progenitors obtained from late gestation and adult mice, whose differentiation only occurred in the absence of IL-7. The newly in vitro–generated B cells of the early embryo cell lines repopulated adult immunodeficient severe combined immunodeficient mice on their adoptive transfer in vivo and generated specific humoral immune responses after immunization.
FLT3 internal tandem duplication mutations associated with human acute myeloid leukemias induce myeloproliferative disease in a murine bone marrow transplant model
Authors: Kelly Louise M. , Liu Qing , Kutok Jeffrey L. , Williams Ifor R. , Boulton Christina L. , Gilliland D. Gary
Published: July 2002

FLT3 receptor tyrosine kinase is expressed on lymphoid and myeloid progenitors in the hematopoietic system. Activating mutations in FLT3 have been identified in approximately 30% of patients with acute myelogenous leukemia, making it one of the most common mutations observed in this disease. Frequently, the mutation is an in-frame internal tandem duplication (ITD) in the juxtamembrane region that results in constitutive activation of FLT3, and confers interleukin-3 (IL-3)–independent growth to Ba/F3 and 32D cells. FLT3-ITD mutants were cloned from primary human leukemia samples and assayed for transformation of primary hematopoietic cells using a murine bone marrow transplantation assay. FLT3-ITDs induced an oligoclonal myeloproliferative disorder in mice, characterized by splenomegaly and leukocytosis. The myeloproliferative phenotype, which was associated with extramedullary hematopoiesis in the spleen and liver, was confirmed by histopathologic and flow cytometric analysis. The disease latency of 40 to 60 days with FLT3-ITDs contrasted with wild-type FLT3 and enhanced green fluorescent protein (EGFP) controls, which did not develop hematologic disease (> 200 days). These results demonstrate that FLT3-ITD mutant proteins are sufficient to induce a myeloproliferative disorder, but are insufficient to recapitulate the AML phenotype observed in humans. Additional mutations that impair hematopoietic differentiation may be required for the development of FLT3-ITD–associated acute myeloid leukemias. This model system should be useful to assess the contribution of additional cooperating mutations and to evaluate specific FLT3 inhibitors in vivo.
2‐dodecyl‐6‐methoxycyclohexa‐2,5‐diene‐1,4‐dione mediates the effect of ROS‐enhanced PI3K/Akt/mTOR pathway on autophagy in breast cancer
Authors: Chen Linqian , Chen Meifeng , Xie Yan , Zhang Yuyan , Mo Shutian , He Yongfei , Liang Tianyi , Liao Yuan , Huang Renbin , Huang Guodong , Han Chuangye , Pham Thi Thai Hoa
Published: December 2024

Several studies have suggested a potential antitumor effect of 2‐dodecyl‐6‐methoxycyclohexa‐2,5‐diene‐1,4‐dione (DMDD). To further understand the mechanism of action of this compound, we investigated its effect on the phosphatidylinositol‐3‐kinase (PI3K)/serine–threonine kinase (Akt)/mammalian target of rapamycin (mTOR) signaling pathway. We show that DMDD application significantly inhibited the proliferation of breast cancer cell lines MDA‐MB‐231 and ER‐α positive MCF‐7. Furthermore, DMDD application resulted in increased intracellular reactive oxygen species (ROS) levels, apoptosis and autophagy, whereas it downregulated the expression of PI3K, Akt and mTOR mRNA and proteins, and increased the expression of LC3II/I and p62 proteins. In a mouse breast cancer xenograft model, DMDD inhibited tumor growth. Expression analyses suggest that ROS levels were higher in DMDD treated tumor tissues, whereas immunohistochemical analyses suggest that apoptotic cells were more prevalent in the DMDD treated group compared to the control group. Taken together, our results suggest that the molecular mechanism of action of DMDD may involve the enhancement of breast cancer autophagy through the PI3K/Akt/mTOR signaling pathway by mediating ROS expression.
Measuring Frailty in Systemic Lupus Erythematosus
Authors: Katz Patricia , Dall'Era Maria , Plantinga Laura , Barbour Kamil E. , Greenlund Kurt J. , Yazdany Jinoos
Published: December 2024

Objective

Recent research has explored frailty in systemic lupus erythematosus using multiple measures. We examined the agreement among frailty measures and the association of each with cross‐sectional and longitudinal health outcomes.

Methods

We used data from the California Lupus Epidemiology Study to examine the following measures of frailty: Systemic Lupus International Collaborating Clinics (SLICC) Frailty Index (SLICC‐FI), Short Physical Performance Battery (SPPB), and Fatigue, Resistance, Ambulation, Illness, and Loss of Weight (FRAIL) scale questionnaire. Patient‐Reported Outcomes Measurement Information System Physical Function 10a (PF) was tested as a proxy measure of frailty. Agreement between frailty classifications by each measure was assessed. Cross‐sectional associations of frailty classifications with hospitalization, valued life activities disability, cognitive impairment, six‐minute walk test distance, self‐reported disease damage, fatigue, and depressive symptoms were assessed with logistic and linear regression analyses. Associations with hospitalization, disease damage increase, and disability increase over the subsequent three years were assessed by Cox proportional hazards analyses.

Results

Percentages of participants identified as frail varied among the measures, from 10.8% to 45.9%. Agreement among classifications ranged from slight to substantial (k from 0.17 to 0.63). Most of the frailty measures were associated with both cross‐sectional and longitudinal health outcomes, with the notable exception of the SPPB. SLICC‐FI had the most consistent association with outcomes, followed by FRAIL and PF.

Conclusion

Multiple measures of frailty appear to identify the risk of poor health outcomes. The intended use, as well as the simplicity and practicality of implementing the measure, may be the most important considerations in choosing a frailty measure.
A Single‐Atom Interface Engineering Strategy to Promote Hydrogen Sorption Performances of Magnesium Hydride
Authors: Li Yinghui , Ren Li , Yao Yingying , Zhao Yingyan , Xu Hao , Li Zhao , Li Zi , dai Xiaohan , Tian Yuhan , Cao Shusheng , Lin Xi , Ye Chongnan , Züttel Andreas , Zou Jianxin
Published: December 2024

Magnesium hydride (MgH2) is regarded as a promising hydrogen storage material owing to its high gravimetric and volumetric capacity and low cost. However, its large‐scale application is hampered by high stability leading to elevated temperature and slow kinetics for ab/desorption. To address these problems, herein, a composite having MgH2 nanoconfined in a 3D nickel single atoms doped porous carbon (MgH2@3D Ni SA‐pC) is successfully prepared. Benefitting from the nondestructive synthetic method, strong coupling between MgH2 and 3D Ni SA‐pC is achieved, and the composite exhibits superior hydrogen sorption performances as compared to blank MgH2. An onset desorption temperature down to 170 °C and the complete dehydrogenation at 250 °C within 60 min are observed. In particular, thermodynamics of MgH2 is improved (ΔHab = 67.9 kJ mol−1 H2) and the heterogenous interfaces are stable during cycling without the formation of an intermetallic Mg2Ni catalytic phase. Experimental characterizations and theoretical calculations show that the robust interfaces induce charge transfer from Mg/MgH2 to Ni SA‐pC, which contributes to the weakened Mg─H bonds and thereby improves kinetic and even thermodynamics. Such an interface engineering strategy using single‐atom Ni catalyst to simultaneously nano‐confine and catalyze MgH2 paves a way to the design of high‐performance hydrogen storage materials.