bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subpial and stellate cells: Two populations of interneurons in turtle visual cortex
Authors: Colombe Jeffrey B. , Sylvester Juliesta , Block Joseph , Ulinski Philip S. 
Published: February 2004

AbstractTurtle visual cortex has three layers and receives direct input from the dorsolateral geniculate complex of the thalamus. The outer layer 1 contains several populations of interneurons, but their physiological properties have not been characterized. This study used intracellular recording methods followed by filling with Neurobiotin to characterize the morphology and physiology of two populations of layer 1 interneurons. Subpial cells have somata positioned in the outer third of layer 1 and dendrites confined within the band of geniculate afferents that runs from lateral to medial across visual cortex. Their dendrites are composed of a sequence of many beads or varicosities separated by intervaricose segments. They have membrane time constants of τo = 45.5 ± 5.2 ms and electrotonic lengths of 1.1 ± 0.2. Subpial cells show spike rate adaptation in response to intracellular current pulses. Stellate cells have somata located in the inner two‐thirds of layer 1 and, less frequently, in layers 2 and 3. Their dendrites extend in a stellate configuration across the cortex. They are smooth or sparsely spiny, but never bear distinct varicosities. They have membrane time constants of τo = 155.1 ± 12 ms and electrotonic lengths of 3.8 ± 0.5. They show little spike rate adaptation in response to intracellular current pulses. The positions of the two populations of cells in visual cortex and their physiological properties suggest that subpial cells may participate in a feedforward inhibitory pathway to pyramidal cells, whereas stellate cells are involved in feedback inhibition to pyramidal cells. J. Comp. Neurol. 471:333–351, 2004. © 2004 Wiley‐Liss, Inc.
The inner ear of the lungfish Protopterus
Authors: Platt Christopher , Jørgensen Jørgen M. , Popper Arthur N. 
Published: February 2004

AbstractThe sensory end organs of the inner ear of the lungfish, Protopterus, were examined using scanning and transmission electron microscopy. The utricle has a structure and hair cell orientation pattern that are typical for vertebrates, although the hair cells are unusually large. There are the typical three semicircular canals extending from the utricle, with the typical hair cell orientations, but the lateral canal sensory crista looks like the “hemicrista” of some amphibians and amniotes, lacking a saddle‐shaped flare on one wall of the ampulla. Unlike most vertebrates that have the saccule and lagena as two separate pouches ventral to the utricle, the lungfish has a single large ventral pouch that contains a single large pasty otoconial mass. This mass covers two hair cell patches, each like a striola with prominent hair cell ciliary bundles, that are presumed to represent saccular and lagenar maculae. However, these two major sensory patches are not completely separate maculae because they lie within a less densely populated field of smaller hair cells, which forms an extrastriolar region that surrounds and fills the region between the two striolae of higher hair cell density. The more caudal lagenar striola is a vertically elongated stripe with hair cell orientation vectors facing antiparallel on either side of a midline drawn vertically along the macula, resembling the macula lagena of some bony fishes but not of tetrapods. The more rostral saccular striola is a curving band with hair cell orientation vectors facing away from its midline, but because this macula curves in three dimensions, the vectors at the rostral end of this striola are oriented mediolaterally, whereas the vectors on the caudal half of this striola are oriented dorsoventrally. The presence of a macula neglecta was confirmed near the posterior canal as a tiny single patch of a few dozen hair cells with all the cell orientations directed caudally. The ciliary bundles on the cells in the striolar‐like regions of all of three otolithic organs average over 80 cilia, a number far greater than for any other fish studied to date. The features of the single sacculolagenar pouch with separate striolar‐like regions, the cellular orientation in the otolith organs, and the large cells and ciliary bundles in Protopterus also were observed in specimens of the other extant lungfish genera, Lepidosiren and Neoceratodus. J. Comp. Neurol. 471:277–288, 2004. © 2004 Wiley‐Liss, Inc.
Synaptic structural modification following changes in activity induced by tetanus neurotoxin in cat abducens neurons
Authors: González‐Forero David , Pastor Angel M. , Delgado‐García Jose María , de la Cruz Rosa R. , Alvarez Francisco J. 
Published: February 2004

AbstractA low or a high dose of tetanus neurotoxin (TeNT) injected in the lateral rectus muscle of the cat causes respectively, functional block of inhibitory synapses only or of both inhibitory and excitatory synapses simultaneously in abducens neurons (González‐Forero et al. [2003] J. Neurophysiol. 89:1878–1890). As a consequence, neuronal firing activity increases (at low dose) or decreases (at high dose). We investigated possible structural modifications of inhibitory synapses in response to these activity alterations induced by TeNT. We used immunofluorescence against postsynaptic (gephyrin) and presynaptic (vesicular γ‐aminobutyric acid [GABA] transporter [VGAT]) markers of inhibitory synapses in combination with cell type markers for abducens motoneurons (calcitonin gene‐related peptide or choline acetyltransferase) or internuclear neurons (calretinin). Seven days after high‐dose treatment, the number of gephyrin‐immunoreactive (IR) clusters per 100 μm of membrane perimeter was reduced on the soma of abducens motoneurons by 55.3% and by 60.1% on internuclear neurons. Proximal dendritic gephyrin‐IR clusters were also significantly altered but to a lesser degree. Partial synaptic re‐establishment was observed 15 days post injection, and complete recovery occurred after 42 days. Coverage by VGAT‐IR terminals was reduced in parallel. In contrast, a low dose of TeNT caused no structural alterations. With electron microscopy we estimated that overall synaptic coverage was reduced by 40% in both types of neurons after a high dose of TeNT. However, F‐type terminals with postsynaptic gephyrin were preferentially lost. Thus, the ratio between F and S terminals diminished from 1.28 to 0.39 on motoneurons and from 1.26 to 0.47 on internuclear neurons. These results suggest that the maintenance of proximal inhibitory synaptic organization on central neurons is best related to neuronal activity and not to the level of inhibitory synaptic function, which was equally blocked by the high or low dose of TeNT. J. Comp. Neurol. 471:201–218, 2004. © 2004 Wiley‐Liss, Inc.
Somatotopic organization and functional properties of mechanosensory neurons expressing sensorin‐A mRNA in Aplysia californica
Authors: Walters Edgar T. , Bodnarova Michaela , Billy Allen J. , Dulin Michael F. , Díaz‐Ríos Manuel , Miller Mark W. , Moroz Leonid L. 
Published: February 2004

AbstractA previous study reported that a peptide, sensorin‐A, is expressed exclusively in mechanosensory neurons having somata in central ganglia of Aplysia. The present study utilized in situ hybridization, staining by nerve back‐fill and soma injection, and electrophysiological methods to characterize the locations, numbers, and functions of sensorin‐A‐expressing neurons and to define the relationships between soma locations and the locations of peripheral axons and receptive fields. Approximately 1,000 cells express sensorin‐A mRNA in young adult animals (10–30 g) and 1,200 cells in larger adults (100–300 g). All of the labeled somata are in the CNS, primarily in the abdominal LE, rLE, RE and RF, pleural VC, cerebral J and K, and buccal S clusters. Expression also occurs in a few sparsely distributed cells in most ganglia. Together, receptive fields of all these mechanosensory clusters cover the entire body surface. Each VC cluster forms a somatotopic map of the ipsilateral body, a “sensory aplunculus.” Cells in the pleural and cerebral clusters have partially overlapping sensory fields and synaptic targets. Buccal S cells have receptive fields on the buccal mass and lips and display notable differences in electrophysiological properties from other sensorin‐A‐expressing neurons. Neurons in all of the clusters have relatively high mechanosensory thresholds, responding preferentially to threatening or noxious stimuli. Synaptic outputs to target cells having defensive functions support a nociceptive role, as does peripheral sensitization following noxious stimulation, although additional functions are likely in some clusters. Interesting questions arise from observations that mRNA for sensorin‐A is present not only in the somata but also in synaptic regions, connectives, and peripheral fibers. J. Comp. Neurol. 471:219–240, 2004. © 2004 Wiley‐Liss, Inc.
Synaptic interactions between the terminals of slow‐adapting type II mechanoreceptor afferents and neurones expressing γ‐aminobutyric acid‐ and glycine‐like immunoreactivity in the rat spinal cord
Authors: Watson Alan H.D. 
Published: February 2004

AbstractThe object of this study was to analyse the synaptic interactions of slow‐adapting type II (SAII) afferent terminals in laminae III–V of the rat spinal cord. The axons of SAII afferents were physiologically characterized by intracellular recording before injection with neurobiotin and preparation for electron microscopy. Axon terminals were serially sectioned and immunolabelled with antibodies against γ‐aminobutyric acid (GABA) or glycine by using a postembedding immunogold procedure. Computer‐aided reconstruction was used to reveal the relative distribution of different types of synapses on terminal and en passant synaptic boutons. Eighty‐nine percent of boutons received axoaxonic synaptic contacts, the mean number of contacts per bouton being 3.5. Fifty‐nine percent of presynaptic axons were immunoreactive for both GABA and glycine and 45% for GABA alone. Most boutons (95%) made axodendritic contacts, and the mean number of dendrites contacted was 1.6. More than half of the postsynaptic dendrites were greater than 1 μm in diameter. Twenty‐three percent were immunoreactive for glycine, and 71% were not immunoreactive for either antibody. Synaptic triads in which an axon presynaptic to the afferent was also in contact with a dendrite postsynaptic to the afferent were seen at 63% of boutons. These results are discussed in the light of similar studies of other low‐threshold mechanoreceptive afferent terminals in the rat and cat and in the context of what is known of the sensory interneurones carrying information from slow‐ and rapid‐adapting mechanoreceptors. J. Comp. Neurol. 471:168–179, 2004. © 2004 Wiley‐Liss, Inc.
Minimum action method for the study of rare events
Authors: E Weinan , Ren Weiqing , Vanden‐Eijnden Eric 
Published: February 2004

AbstractThe least action principle from the Wentzell‐Freidlin theory of large deviations is exploited as a numerical tool for finding the optimal dynamical paths in spatially extended systems driven by a small noise. The action is discretized and a preconditioned BFGS method is used to optimize the discrete action. Applications are presented for thermally activated reversal in the Ginzburg‐Landau model in one and two dimensions, and for noise induced excursion events in the Brusselator taken as an example of non‐gradient system arising in chemistry. In the Ginzburg‐Landau model, the reversal proceeds via interesting nucleation events, followed by propagation of domain walls. The issue of nucleation versus propagation is discussed and the scaling for the number of nucleation events as a function of the reversal time and other material parameters is computed. Good agreement is found with the numerical results. In the Brusselator, whose deterministic dynamics has a single stable equilibrium state, the presence of noise is shown to induce large excursions by which the system cycles out of this equilibrium state. © 2004 Wiley Periodicals, Inc.
Linear vs. nonlinear selection for the propagation speed of the solutions of scalar reaction‐diffusion equations invading an unstable equilibrium
Authors: Lucia Marcello , Muratov Cyrill B. , Novaga Matteo 
Published: February 2004

AbstractWe revisit the classical problem of speed selection for the propagation of disturbances in scalar reaction‐diffusion equations with one linearly stable and one linearly unstable equilibrium. For a wide class of initial data this problem reduces to finding the minimal speed of the monotone traveling wave solutions connecting these two equilibria in one space dimension. We introduce a variational characterization of these traveling wave solutions and give a necessary and sufficient condition for linear versus nonlinear selection mechanism. We obtain sufficient conditions for the linear and nonlinear selection mechanisms that are easily verifiable. Our method also allows us to obtain efficient lower and upper bounds for the propagation speed. © 2004 Wiley Periodicals, Inc.
On a wave map equation arising in general relativity
Authors: Ringström Hans 
Published: February 2004

AbstractWe consider a class of space‐times for which the essential part of Einstein's equations can be written as a wave map equation. The domain is not the standard one, but the target is hyperbolic space. One ends up with a 1 + 1 nonlinear wave equation, where the space variable belongs to the circle and the time variable belongs to the positive real numbers. The main objective of this paper is to analyze the asymptotics of solutions to these equations as t → ∞. For each point in time, the solution defines a loop in hyperbolic space, and the first result is that the length of this loop tends to 0 as t−1/2 as t → ∞. In other words, the solution in some sense becomes spatially homogeneous. However, the asymptotic behavior need not be similar to that of spatially homogeneous solutions to the equations. The orbits of such solutions are either a point or a geodesic in the hyperbolic plane. In the nonhomogeneous case, one gets the following asymptotic behavior in the upper half‐plane (after applying an isometry of hyperbolic space if necessary):

The solution converges to a point.
The solution converges to the origin on the boundary along a straight line (which need not be perpendicular to the boundary).
The solution goes to infinity along a curve y = const.
The solution oscillates around a circle inside the upper half‐plane.

Thus, even though the solutions become spatially homogeneous in the sense that the spatial variations die out, the asymptotic behavior may be radically different from anything observed for spatially homogeneous solutions of the equations. This analysis can then be applied to draw conclusions concerning the associated class of space‐times. For instance, one obtains the leading‐order behavior of the functions appearing in the metric, and one can conclude future causal geodesic completeness. © 2004 Wiley Periodicals, Inc.
Studying protein folding on the Grid: experiences using CHARMM on NPACI resources under Legion
Authors: Natrajan Anand , Crowley Michael , Wilkins‐Diehr Nancy , Humphrey Marty A. , Fox Anthony D. , Grimshaw Andrew S. , Brooks Charles L. 
Published: February 2004

AbstractOne benefit of a computational Grid is the ability to run high‐performance applications over distributed resources simply and securely. We demonstrated this benefit with an experiment in which we studied the protein‐folding process with the CHARMM molecular simulation package over a Grid managed by Legion, a Grid operating system. High‐performance applications can take advantage of Grid resources if the Grid operating system provides both low‐level functionality as well as high‐level services. We describe the nature of services provided by Legion for high‐performance applications. Our experiences indicate that human factors continue to play a crucial role in the configuration of Grid resources, underlying resources can be problematic, Grid services must tolerate underlying problems or inform the user, and high‐level services must continue to evolve to meet user requirements. Our experiment not only helped a scientist perform an important study, but also showed the viability of an integrated approach such as Legion's for managing a Grid. Copyright © 2004 John Wiley & Sons, Ltd.
Genetically induced communication network fault tolerance
Authors: Bush Stephen F. 
Published: February 2004

AbstractThis article presents the architecture and initial feasibility results of a proto‐type communication network that utilizes genetic programming to evolve services and protocols as part of network operation. The network evolves responses to environmental conditions in a manner that could not be pre‐programmed within legacy network nodes a priori. A priori in this case means before network operation has begun. Genetic material is exchanged, loaded, and run dynamically within an active network. The transfer and execution of code in support of the evolution of network protocols and services would not be possible without the active network environment. Rapid generation of network service code occurs via a genetic programming paradigm. Complexity and algorithmic information theory play a key role in understanding and guiding code evolution within the network. © 2004 Wiley Periodicals, Inc. Complexity 9: 19–33, 2004
Beyond anarchy: Self‐organized topology for peer‐to‐peer networks
Authors: Saffre Fabrice , Ghanea‐Hercock Robert 
Published: February 2004

AbstractIn this article, we discuss the new constraints that will apply to future, highly dynamic networks and investigate one of the major problems that is likely to affect their deployment: traffic/workload distribution. Starting with a very simple model, we demonstrate that a structure made of undifferentiated subunits will almost inevitably hit a scalability barrier, unless new design rules are applied. We then give quantitative evidence that a hybrid network topology termed the “hypergrid” could have the potential of solving some of the most critical problems (relay overload and network vulnerability), yet could still be produced by applying local rules only. © 2004 Wiley Periodicals, Inc. Complexity 9: 49–53, 2004
Kolmogorov complexity estimates for detection of viruses in biologically inspired security systems: A comparison with traditional approaches
Authors: Goel Sanjay , Bush Stephen F. 
Published: February 2004

AbstractThis article presents results in two mutually complementary areas: distributed immunological information assurance and a new signature‐matching technique based on Kolmogorov Complexity. This article introduces a distributed model for security based on biological paradigms of epidemiology and immunology. In this model each node in the network has an immune system that identifies and destroys pathogens in the incoming network traffic as well as files resident on the node. The network nodes present a collective defense to the pathogens by working symbiotically and sharing pathogen information with each other. Each node compiles a list of pathogens that are perceived as threats by using information provided from all the nodes in the network. The signatures for these pathogens are incorporated into the detector population of the immune systems to increase the probability of detection. Critical to the success of this system is the detection scheme, which should not only be accurate but also efficient. Three separate schemes for detecting pathogens are examined, namely, contiguous string matching, Hamming distance, and Kolmogorov Complexity. This work provides a model of the system and examines the efficiency of different detection schemes. A simulation model is built to study the sensitivity of model parameters, such as signature length, sampling rate, and network topology, to detection of pathogens. © 2004 Wiley Periodicals, Inc. Complexity 9: 54–73, 2004
Aspects of adaptive reconfiguration in a scalable intrusion tolerant system
Authors: Bryant Stephanie , Wang Feiyi 
Published: February 2004

AbstractAn Erratum has been published for this article in Complexity (2004) 9(4) 46
SITAR architecture integrates basic fault tolerant concepts along with adaptive reconfiguration in a security setting. It enables commercial‐off‐the‐shelf servers to continue operating despite intrusion or partial compromise. The adaptive reconfiguration dynamically changes the system configuration in response to environment threats to maintain service availability. The discussion covers important aspects of SITAR's adaptive reconfiguration mechanism, including its central algorithm, and mitigation of the oscillation problem. The mechanism uses a feedback loop model and techniques of mutual exclusion, steady state monitoring, and system observation to implement cooperative control. The adaptive mechanism is implemented and demonstrated as part of the SITAR prototype system. © 2004 Wiley Periodicals, Inc. Complexity 9: 74–83, 2004
Autonomic defense: Thwarting automated attacks via real‐time feedback control
Authors: Armstrong Derek , Carter Sam , Frazier Gregory , Frazier Tiffany 
Published: February 2004

AbstractA critical threat to organizations, and the Internet itself, is a class of automated network attacks referred to as Internet worms. This article examines the use of mathematical models and optimization algorithms—specifically a partially‐observable Markov decision process (PO‐MDP) based feedback control system—as the basis for implementing an autonomic defense system (ADS) that can protect organizations against Internet worms. The PO‐MDP ADS introduced in this article is capable of detecting and responding to worms in real time. Furthermore, the PO‐MDP ADS can ameliorate the rate of incorrect control decisions that would normally occur in the presence of sensor false alarms. © 2004 Wiley Periodicals, Inc. Complexity 9: 41–48, 2004
Influence of complex formation upon inclusion of Mn(II), Co(II), Ni(II), and Cu(II) in ZnC2O4·2H2O
Authors: Donkova B. , Pencheva J. , Djarova M. 
Published: February 2004

AbstractThe inclusion of 3d‐impurities Mn(II), Co(II), Ni(II) and Cu(II) in a crystalline precipitate of ZnC2O4·2H2O is investigated. This study is a part of the systematic one deal with the mechanism of inclusion of 3d‐ions in sparingly soluble oxalate systems. The experiments are carried out in bi‐ end multi‐component systems at two different mediums – one with deficiency of oxalate ions, another with excess. The insertion of 3d‐ions upon mass crystallization of ZnC2O4·2H2O does not proceed by a simple ionic substitution. The results show that the inserted amount of impurity depends on some physicochemical characteristics of the neutral monooxalato complexes [MnC2O4]o, [CoC2O4]o, [NiC2O4]o and [CuC2O4]o. Good agreement between included impurity and the concentration of its complex in the solution is established. The stability constant of monooxalato complex affects the impurity inclusion. This effect depends on the medium nature. In the deficiency of oxalate ions the factor determining the inclusion is thermodynamic one – stability of monooxalato complexes. In the excess of oxalate ions inserted amount depends on kinetic factor – the formation rate of these complexes. In the term of that the insertion of Mn(II) is definitely different in the two mediums while that of the Ni (II) does not depend on the medium. The copper shows deviation from overall dependence in the two mediums due to the Jahn‐Teller distortion. Its double decreasing insertion in the excess of oxalate ions is related with stabilization of [Cu(C2O4)2]2‐. The conclusions presume that by varying the background medium and taking in view the ions present in the solution, the amount of inserted impurities can be predicted and controlled. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)