bluuebunny/crossref_metadata_2025_split huggingface dataset:
STOCHASTIC RESONANCE AND TIME ADVANCE CODING IN CHEMICAL REACTIONS
Authors: FÖRSTER A. , GUDERIAN A. , ZEYER K.-P. , DECHERT G. , SCHNEIDER F.W. 
Published: October 2004

Stochastic Resonance (SR) is a phenomenon wich may be found in nonlinear systems close to an excitation threshold. SR is a means for enhancing a weak periodic subthreshold signal from its noisy background by adding stochastic fluctuations, i.e. in biological and physical systems. It has been proposed that SR is important for the ability of neural systems to detect weak periodic signals. In the present work we show experimentally that SR occurs in two nonlinear chemical reactions, namely in the enzymatic Peroxidase-Oxidase (PO) reaction and in the Belousov–Zhabotinskii (BZ) reaction. A small sinusoidal signal with increasing noise is imposed on the focal steady state near a subcritical Hopf bifurcation. When the threshold is crossed beyond a certain noise amplitude, the system responds with spikes. The resulting interspike histogram and the plot of the signal to noise ratio, which is evaluated from the respective Fourier spectra, pass through a maximum at an optimal external noise level. An alternative way to cross the excitation threshold without noise is the variation of the bias value of the sinusoidal signal. The variation of the bias value causes the spikes to appear earlier if the sinusoidal function is moved closer towards the threshold. This so-called time advance coding is shown experimentally for the first time in the BZ reaction by imposing sinusoidal flow rate variations using different bias values. The phenomenon has been proposed by Hopfield11 to be a means for analog pattern recognition.
SPONTANEOUS AND EVOKED CORTICAL DYNAMICS DURING DEEP ANAESTHESIA
Authors: MÄKINEN SAKU , HARTIKAINEN KAISA , ERIKSSON JARL-THURE , JÄNTTI VILLE 
Published: October 2004

In this paper we have studied cortical dynamics as assessed using graphical methods during deep anaesthesia. Graphical analysis was carried out by autocorrelation functions and return maps with different lags. During moderate and deep anaesthesia, the electroencephalogram (EEG) shows a burst suppression pattern, consisting of abruptly-occurring high amplitude bursts alternating with periods of relative silence. Deep anaesthesia with burst suppression pattern provides a simple model of brain activity when the noise that is usually present in a subject who is awake is suppressed. During anaesthesia-induced EEG suppression, the brain reacts to different external stimuli with bursts. In respect to sensory processing during anaesthesia, it is interesting to know whether these bursts have different dynamics depending on the stimuli used. We have used graphical analysis to reveal the possible differences in bursts evoked by different stimuli. Externally evoked bursts were induced by auditory, electric and visual stimuli. The EEG studied in this paper consists of 25 bursts from one subject. We have estimated the autocorrelation function for each burst and used the formation gained from such autocorrelation coefficients as the grounds for determining different lags for return maps. The graphical methods used revealed differences in dynamics and topology of bursts as evoked by different stimuli. Spontaneous bursts clearly had different dynamics from evoked burst; which could not be seen directly from the raw EEG data. This study suggests that graphical analysis is a useful tool to obtain information about the dynamics of neuronal processes behind cortical responses during deep anaesthesia.
REAFFERENCE AND ATTRACTORS IN THE OLFACTORY SYSTEM DURING ODOR RECOGNITION
Authors: KAY LESLIE M. , LANCASTER LARRY R. , FREEMAN WALTER J. 
Published: October 2004

Olfactory bulb activity has been postulated to be chaotic, as measured in the EEG, and to be subject to an attractor with many “wings” enabling classification of different learned odor classes. Two parallel questions are thus addressed by the work presented here: (1) what is the evidence for attractors in the olfactory system, which can mediate learned odor classes? and (2) how does the olfactory system enter a specific attractor or attractor wing associated with the learned odor during the classification process? Both of these questions address the wider notion of endogenous activity preparing the system for an expected stimulus, which is at the basis of the reafference principle. By viewing the brain as a distributed complex dynamical system with global attractors, these questions can be answered together. Rats were implanted with bipolar macroelectrodes in the Olfactory Bulb (OB), Prepyriform Cortex (PPC), Entorhinal Cortex (EC), and Dentate Gyrus (DG), and then trained in an operant paradigm to press a bar for a reward in the presence of one odor and to receive no reward in the presence of another odor. Local Field Potentials (LFP) were recorded simultaneously from the structures during the operant task. We present evidence for three endogenous events: (1) preafference, which is manifested both by the EC entering an attractor and a mid-range signal (15–30 Hz) which appears to be passed from the EC to the OB just before the OB enters an attractor; (2) afference, where the OB enters an attractor during the odor recognition period of the experiment and the LFP recordings indicate that the OB drives the other structures in all frequency bands, especially the high gamma band (65–100 Hz) associated with the OB burst frequency; and (3) reafference or post-afference, which is accompanied by a lower frequency gamma band signal (40–60 Hz) originating in the PPC and passed to both the OB and the EC just before the onset of the motor response to the odor. We use a new method, NECTAR (Nonparametric Exact Contingency Table Association Routine), related to mutual information, to verify what is seen with coherence and phase estimates, the apparent driving of each structure at different times in the odor trials, and to display evidence for non-periodic attractors governing both individual physiological structures and the system of structures. This is the first evidence of an endogenous, limbic event associated with sensory perceptual tuning in a mammal. These results are also the first experimental confirmation that the attractors governing olfactory activity involve multiple sites in the olfactory/limbic system and implement the process of attention.
ON THE LOCAL-FIELD DISTRIBUTION IN ATTRACTOR NEURAL NETWORKS
Authors: KORUTCHEVA E. , KOROUTCHEV K. 
Published: October 2004

In this paper a simple two-layer neural network's model, similar to that studied by D. Amit and N. Brunel,11 is investigated in the frames of the mean-field approximation. The distributions of the local fields are analytically derived and compared to those obtained in Ref. 11. The dynamic properties are discussed and the basin of attraction in some parametric space is found. A procedure for driving the system into a basin of attraction by using a regulation imposed on the network is proposed. The effect of outer stimulus is shown to have a destructive influence on the attractor, forcing the latter to disappear if the distribution of the stimulus has high enough variance or if the stimulus has a spatial structure with sufficient contrast. The techniques, used in this paper, for obtaining the analytical results can be applied to more complex topologies of linked recurrent neural networks.
HYPER-SYSTOLIC PROCESSING ON APE100/QUADRICS: n2-LOOP COMPUTATIONS
Authors: LIPPERT THOMAS , RITZENHÖFER GERO , GLAESSNER UWE , HOEBER HENNING , SEYFRIED ARMIN , SCHILLING KLAUS 
Published: October 2004

We investigate the performance gains from hyper-systolic implementations of n2-loop problems on the massively parallel computer Quadrics, exploiting its three-dimensional interprocessor connectivity. For illustration we study the communication aspects of an exact molecular dynamics simulation of n particles with Coulomb (or gravitational) interactions. We compare the interprocessor communication costs of the standard-systolic and the hyper-systolic approaches for various granularities. We predict gain factors as large as three on the Q4 and eight on the QH4 and measure actual performances on these machine configurations. We conclude that it appears feasible to investigate the thermodynamics of a full gravitating n-body problem with O(16.000) particles using the new method on a QH4 system.
CLUSTER CONCEPT DYNAMICS LEADING TO CREATIVE IDEAS WITHOUT CRITICAL SLOWING DOWN
Authors: GOLDENBERG Y. , SOLOMON S. , MAZURSKY D. 
Published: October 2004

We present algorithmic procedures for generating systematically ideas and solutions to problems which are perceived as creative. Our method consists of identifying and characterizing the most creative ideas among a vast pool. We show that they fall within a few large classes (archetypes) which share the same conceptual structure (Macros). We prescribe well defined abstract algorithms which can act deterministically on arbitrary given objects. Each algorithm generates ideas with the same conceptual structure characteristic to one of the Macros. The resulting new ideas turn out to be perceived as highly creative. We support our claims by experiments in which senior advertising professionals graded advertisement ideas produced by our method according to their creativity. The marks (grade 4.6±0.2 on a 1–7 scale) obtained by laymen applying our algorithms (after being instructed for only two hours) were significantly better than the marks obtained by advertising professionals using standard methods (grade 3.6±0.2)). The method, which is currently taught in USA, Europe, and Israel and used by advertising agencies in Britain and Israel has received formal international recognition.
SPONTANEOUS SCALING EMERGENCE IN GENERIC STOCHASTIC SYSTEMS
Authors: SOLOMON SORIN , LEVY MOSHE 
Published: October 2004

We extend a generic class of systems which have previously been shown to spontaneously develop scaling (power law) distributions of their elementary degrees of freedom. While the previous systems were linear and exploded exponentially for certain parameter ranges, the new systems fulfill nonlinear time evolution equations similar to the ones encountered in Spontaneous Symmetry Breaking (SSB) dynamics and evolve spontaneously towards "fixed trajectories" indexed by the average value of their degrees of freedom (which corresponds to the SSB order parameter). The "fixed trajectories" dynamics evolves on the edge between explosion and collapse/extinction. The systems present power laws with exponents which in a wide range (α < –2.) are universally determined by the ratio between the minimal and the average values of the degrees of freedom. The time fluctuations are governed by Levy distributions of corresponding power. For exponents α > −2 there is no "thermodynamic limit" and the fluctuations are dominated by a few, largest degrees of freedom which leads to macroscopic fluctuations, chaos, and bursts/intermittency.
DISTINGUISHING MUTANTS BY KNOT POLYNOMIALS
Authors: MORTON HUGH R. , CROMWELL PETER R. 
Published: October 2004

We consider the problem of distinguishing mutant knots using invariants of their satellites. We show, by explicit calculation, that the Homfly polynomial of the 3-parallel (and hence the related quantum invariants) will distinguish some mutant pairs. Having established a condition on the colouring module which forces a quantum invariant to agree on mutants, we explain several features of the difference between the Homfly polynomials of satellites constructed from mutants using more general patterns. We illustrate this by our calculations; from these we isolate some simple quantum invariants, and a framed Vassiliev invariant of type 11, which distinguish certain mutants, including the Conway and Kinoshita-Teresaka pair.
TWO-DIMENSIONAL TOPOLOGICAL QUANTUM FIELD THEORIES AND FROBENIUS ALGEBRAS
Authors: ABRAMS LOWELL 
Published: October 2004

We characterize Frobenius algebras A as algebras having a comultiplication which is a map of A-modules. This characterization allows a simple demonstration of the compatibility of Frobenius algebra structure with direct sums. We then classify the indecomposable Frobenius algebras as being either “annihilator algebras” — algebras whose socle is a principal ideal — or field extensions. The relationship between two-dimensional topological quantum field theories and Frobenius algebras is then formulated as an equivalence of categories. The proof hinges on our new characterization of Frobenius algebras. These results together provide a classification of the indecomposable two-dimensional topological quantum field theories.
THE RESHETIKHIN-TURAEV REPRESENTATION OF THE MAPPING CLASS GROUP AT THE SIXTH ROOT OF UNITY
Authors: WRIGHT GRETCHEN 
Published: October 2004

The quantum group construction of Reshetikhin and Turaev provides representations of the mapping class group, indexed by an integer parameter r. This paper presents computations of these representations when r=6, and analyzes their relationship to other topological invariants. It is shown that in genus 2, the representation splits into two summands. The first summand factors through the mapping class group action on the first homology of the surface with Z/3Z coefficients, while the second summand can be analyzed via its restriction to the subgroup of the mapping class group which is normally generated by the sixth power of a Dehn twist on a nonseparating curve. This analysis reveals a connection to the homology intersection pairing on the surface, and also yields information about the kernel and image of the representation. It is also shown that the representation yields a family of 2-dimensional nonabelian representations of the Torelli group. This paper continues the program established by the author in [Wr] to relate the Reshetikhin-Turaev representations at specific roots of unity to classical invariants.
DECOHERENCE CAUSED BY TOPOLOGY IN A TIME-MACHINE SPACETIME
Authors: MENSKY MICHAEL B. , NOVIKOV IGOR D. 
Published: October 2004

Nonrelativistic quantum theory of noninteracting particles in the spacetime containing a region with closed time-like curves (time-machine spacetime) is considered with the help of the path-integral technique. It is argued that, in certain conditions, a sort of superselection may exist for evolution of a particle in such a spacetime. All types of evolution are classified by the number n defined as the number of times the particle returns back to its past. It corresponds also to the topological class [Formula: see text] of trajectories of a particle. The evolutions corresponding to different values of n are noncoherent. The amplitudes corresponding to such evolutions may not be superposed. Instead of one evolution operator, as in the conventional (coherent) description, evolution of the particle is described by a family Un of partial evolution operators. This is done in analogy with the formalism of quantum theory of measurements, but with essential new features in the dischronal region (the region with closed time-like curves) of the time-machine spacetime. Partial evolution operators Un are equal to integrals Kn over the classes of paths [Formula: see text] if the evolution begins and ends in the chronal regions. If the evolution begins or/and ends in the dischronal region, the integral Kn over the class [Formula: see text] should be multiplied by a certain projector to give the partial evolution operator Un. Thus defined partial evolution operators possess the property of generalized unitarity ∑nUn†Un=1 and multiplicativity Um(t″, t′)Un(t′, t)=Um+n(t″, t). In the last equation however one of the numbers m or n (or both) must be equal to zero. Therefore, the part of evolution containing repeated returning backward in time cannot be factorized: all backward passages of the particle have to be considered as a single act, that cannot be presented as gradually, step by step, passing through “causal loops.” The (generalized) multiplicativity and unitarity take place for arbitrary time intervals including (i) propagating in initial and final chronal regions (containing no time-like closed curves) or from the initial chronal region to the final one, and (ii) propagating within the time machine (in the dischronal region), from the time machine to the final chronal region or from the initial chronal region to the time machine.
QUASIPARTICLE AND PHONON EXCITATIONS IN ODD-MASS N=83 ISOTONES
Authors: LOSANO L. , DIAS H. 
Published: October 2004

The structure of low-lying states in odd-mass N=83 isotones (135≤A≤151) is investigated in terms of a model in which one neutron-quasiparticle is coupled to quadrupolar and octupolar core-vibrations. Energy levels and spectroscopic factors are calculated and compared with experimental data. Nuclear Structure: 135 Te , 137 Xe , 139 Ba , 141 Ce , 143 Nd , 145 Sm , 147 Gd , 149 Dy , and 151 Er ; calculated levels J, π, and S. Quasiparticle-phonon coupling model.
Uterine Spiral Artery Remodeling Involves Endothelial Apoptosis Induced by Extravillous Trophoblasts Through Fas/FasL Interactions
Authors: Ashton Sandra V. , Whitley Guy St. J. , Dash Philip R. , Wareing Mark , Crocker Ian P. , Baker Philip N. , Cartwright Judith E. 
Published: October 2004

Objective—Invasion of uterine spiral arteries by extravillous trophoblasts in the first trimester of pregnancy results in loss of endothelial and musculoelastic layers. This remodeling is crucial for an adequate blood supply to the fetus with a failure to remodel implicated in the etiology of the hypertensive disorder preeclampsia. The mechanism by which trophoblasts induce this key process is unknown. This study gives the first insights into the potential mechanisms involved.Methods and Results—Spiral arteries were dissected from nonplacental bed biopsies obtained at Caesarean section, and a novel model was used to mimic in vivo events. Arteries were cultured with trophoblasts in the lumen, and apoptotic changes in the endothelial layer were detected after 20 hours, leading to loss of endothelium by 96 hours. In vitro, coculture experiments showed that trophoblasts stimulated apoptosis of primary decidual endothelial cells and an endothelial cell line. This was blocked by caspase inhibition and NOK2, a FasL blocking antibody. NOK2 also abrogated trophoblast-induced endothelial apoptosis in the vessel model.Conclusions—Extravillous trophoblast induction of endothelial apoptosis is a possible mechanism by which the endothelium is removed, and vascular remodeling may occur in uterine spiral arteries. Fas/FasL interactions have an important role in trophoblast-induced endothelial apoptosis.
Reduced Macrophage Apoptosis Is Associated With Accelerated Atherosclerosis in Low-Density Lipoprotein Receptor-Null Mice
Authors: Liu June , Thewke Douglas P. , Su Yan Ru , Linton MacRae F. , Fazio Sergio , Sinensky Michael S. 
Published: October 2004

Objective—The majority of apoptotic cells in atherosclerotic lesions are macrophages. However, the pathogenic role of macrophage apoptosis in the development of atherosclerosis remains unclear. Elevated expression of Bax, one of the pivotal proapoptotic proteins of the Bcl-2 family, has been found in human atherosclerotic plaques. Activation of Bax also occurs in free cholesterol-loaded and oxysterol-treated mouse macrophages. In this study, we examined the effect of Bax deficiency in bone marrow-derived leukocytes on the development of atherosclerosis in low-density lipoprotein receptor-null (LDLR−/−) mice.Methods and Results—Fourteen 8-week-old male LDLR−/− mice were lethally irradiated and reconstituted with either wild-type (WT) C57BL6 or Bax-null (Bax−/−) bone marrow. Three weeks later, the mice were challenged with a Western diet for 10 weeks. No differences were found in the plasma cholesterol level between the WT and Bax−/− group. However, quantitation of cross sections from proximal aorta revealed a 49.2% increase (P=0.0259) in the mean lesion area of the Bax−/− group compared with the WT group. A 53% decrease in apoptotic macrophages in the Bax−/− group was found by TUNEL staining (P<0.05).Conclusions—The reduction of apoptotic activity in macrophages stimulates atherosclerosis in LDLR−/− mice, which is consistent with the hypothesis that macrophage apoptosis suppresses the development of atherosclerosis.
Extent and Distribution of White Matter Hyperintensities in Stroke Patients
Authors: Wen Wei , Sachdev Perminder S. 
Published: October 2004

Background and Purpose—White matter hyperintensities (WMHs) on T2-weighted MRI are common in stroke patients and healthy elderly individuals. The detailed anatomical distribution of these lesions in stroke patients has not been examined.Methods—A total of 112 stroke or transient ischemic attack patients and 87 matched control subjects from the Sydney Stroke Study underwent MRI scans that included a T2-weighted fluid-attenuated inversion recovery (FLAIR) sequence. WMHs were delineated from each FLAIR MRI by an automated method. Region of interest and voxel-wise statistical parametric mapping approaches were applied to examine the volume, distribution, and severity of WMHs of the patient and control groups, and subgroups with large or lacunar infarcts.Results—Stroke subjects had significantly more WMHs than controls in all brain regions except the occipital lobe and in all arterial territories except the anterior callosal and anterior medial lenticulostriate. In the frontotemporal regions, average WMH volumes in patients were >3.5× those in controls. The total number of discrete WMHs was not different in the 2 groups, but stroke patients had more large (>20 mm) and high-intensity lesions. Subjects with lacunar infarcts had more WMHs than those with large infarcts, who, in turn, had more WMHs than control subjects. Lacunar infarction subjects had more WMHs than subjects with large thromboembolic or cardioembolic strokes. Those with anterior arterial territory infarction had more WMHs in the frontal regions. Subjects with single or multiple lacunes did not differ in volumes of WMHs.Conclusions—Stroke patients have significantly more WMHs in nearly every brain region than healthy controls. Those with lacunar infarcts are particularly affected. WMHs represent a significant proportion of the ischemic lesion burden in stroke and transient ischemic attack patients.
IFN-γ gene polymorphisms associate with development of EBV+ lymphoproliferative disease in hu PBL-SCID mice
Authors: Dierksheide Julie E. , Baiocchi Robert A. , Ferketich Amy K. , Roychowdhury Sameek , Pelletier Ronald P. , Eisenbeis Charles F. , Caligiuri Michael A. , VanBuskirk Anne M. 
Published: October 2004

AbstractPosttransplantation lymphoproliferative disorder (PTLD) is a devastating post-transplantation complication often associated with Epstein-Barr virus (EBV). Although the type and length of immunosuppression are risk factors, a patient's inherent immune capacity also likely contributes to this disorder. This report uses severe-combined immunodeficient mice given injections of human peripheral blood leukocytes (hu PBL-SCID [Severe Combined Immunodeficient] mice) to test the hypothesis that cytokine genotype associates with the development of EBV-associated lymphoproliferative disease (LPD). We observed that the A/A (adenosine/adenosine) genotype for base + 874 of the interferon γ (IFN-γ) gene was significantly more prevalent in PBLs producing rapid, high-penetrance LPD in hu PBL-SCID mice, compared to PBLs producing late, lowpenetrance LPD or no LPD. In examining the relationship between genotype and cytolytic T-lymphocyte (CTL) function, transforming growth factor β (TGF-β) inhibited restimulation of CTLs in PBLs with adenosine at IFNG base + 874, but not in PBLs homozygous for thymidine. Importantly, neutralization of TGF-β in hu PBL-SCID mice injected with A/A genotype PBLs resulted in reduced LPD development and expanded human CD8+ cells. Thus, our data show that TGF-β may promote tumor development by inhibiting CTL restimulation and expansion. Further, our data indicate that IFNG genotype may provide valuable information for both identifying transplant recipients at greater risk for PTLD and developing preventive and curative strategies.