bluuebunny/crossref_metadata_2025 huggingface dataset:
Prostaglandin-independent effects of aspirin on cell cycle and putrescine synthesis in human colon carcinoma cells
Authors: Eklou-Kalonji E , Andriamihaja M , Reinaud P , Mayeur C , Camous S , Robert V , Charpigny G , Blachier F
Published: June 2003

Aspirin consumption has been reported to be able to reduce colorectal cancer risk in humans and in animal models of colon carcinogenesis. Although the mechanism involved in such an effect is not yet clear, both prostaglandin-dependent and -independent effects have been proposed. Using HT-29 Glc/+cells, which originate from a human colon adenocarcinoma, we demonstrated in this study a dose-dependent effect of millimolar concentration of aspirin on cell growth that was concomitant with a rapid accumulation of the cells in the Go/G1 phase, followed by an accumulation in the G2/M phase and by a minor increase in the proportion of cells undergoing nuclear condensation. Cell membrane integrity and cell release into the culture medium were not affected by this treatment. The aspirin effects were apparently unrelated to prostaglandin biosynthesis inhibition, since although these cells were found to express high levels of cyclooxygenase 1 (COX-1) and low levels of COX-2 proteins, they did not produce any measurable net amounts of prostaglandins, based on both utilization of radiolabelled arachidonic acid and the radioimmunoassay of prostaglandins E2 and F2α. In contrast, we identified polyamine biosynthesis as a cellular target of aspirin, since the treatment of HT-29 Glc/+ cells with aspirin reduced the flux of L-ornithine through ornithine decarboxylase, an effect that could not be explained by an acute action of the drug on the ornithine decarboxylase catalytic activity. Since polyamine biosynthesis is strictly necessary for HT-29 cell growth, our data suggest that reduced flux through ornithine decarboxylase may participate in the antiproliferative activity of aspirin towards colonic tumoral cells. It is concluded that in HT-29 Glc/+ cells that are not functional for prostaglandin production, aspirin can affect cell growth, cell cycle, and polyamine biosynthesis without affecting cell membrane integrity.Key words: aspirin, HT-29 cells, cell cycle, prostaglandins, polyamines.
Aerobic conditioning effects on substrate responses during graded cycling in pregnancy
Authors: Wolfe Larry A , Heenan Aaron P , Bonen Arend
Published: June 2003

This study was conducted to test the hypothesis that aerobic conditioning prevents exercise-induced hypoglycemia and preserves the capacity to utilize carbohydrates and to produce lactate during heavy exercise in late gestation. The effects of closely monitored cycle ergometer conditioning (heart rate = 143 ± 2 beats/min, 25 min/day, 3 days/week) during the second and third trimesters were studied in 18 previously sedentary women (exercised group, EG). A nonexercising pregnant control group (CG, n = 9) was also studied. Data collection times for both groups were as follows: start of the second trimester (Entry), ends of the second (TM2) and third (TM3) trimesters (post-training), and 46 months postpartum (nonpregnant control). Respiratory gas exchange was studied and venous blood samples were obtained before, during, and after a graded cycle ergometer test that was terminated at a peak heart rate of 170 beats/min. Measurements included plasma glucose, insulin, free fatty acids, the respiratory exchange ratio at peak exercise, and peak postexercise lactate concentration. A significant aerobic conditioning effect in the EG was confirmed by a 17% increase in O2pulse at peak exercise between Entry and TM3. As expected, values for free fatty acids in the CG rose with advancing gestational age. The CG showed a clear trend for a rise in plasma insulin with advancing gestational age, under all experimental conditions. Also, peak exercise respiratory exchange ratio and peak postexercise lactate concentration were significantly reduced in late gestation, and plasma glucose decreased significantly during and following the end of TM3 testing. Effects of pregnancy to reduce peak postexercise lactate and to reduce plasma glucose during and after exercise at the end of the third trimester were significantly attenuated in the EG. These effects were attributed to attenuation of pregnancy-induced insulin resistance (as reflected by insulin/glucose ratio) by physical conditioning. These findings support our original experimental hypothesis that aerobic conditioning prevents exercise-induced hypoglycemia and preserves the ability to utilize carbohydrate and produce lactate during heavy exercise in late gestation.Key words: exercise testing, human gestation, carbohydrate metabolism, postexercise hypoglycemia, blood lactate accumulation.
Possible role of nicaraven in neuroprotective effect on hippocampal slice culture
Authors: Yoshinaga Hisao , Watanabe Michiko , Manome Yoshinobu
Published: June 2003

Nicaraven is an agent that is especially beneficial in vasospasm or brain damage caused by subarachnoid hemorrhage. It ameliorates neurological deficits of patients and protects the central nervous system from ischemia. We investigated the neuroprotective effect of nicaraven against oxygenglucose deprivation (OGD) induced or N-methyl-D-aspartic acid (NMDA) induced hippocampal neuronal cell death in organotypic brain slice cultures. The effect of nicaraven on hippocampal neuronal injury was evaluated by inhibition of uptake of propidium iodide (PI) into dead cells. The results demonstrated that nicaraven protected neuronal cells from both OGD- and NMDA-induced cell death. While nicaraven has a strong hydroxyl radical scavenging effect, another radical scavenger, N-acetyl-L-cysteine (NAC), inhibited cell death only caused by OGD. In contrast, the poly(ADP-ribose) synthetase (PARS) inhibitors 3-aminobenzamide (3-AB) and theophylline protected cells from both OGD- and NMDA-induced cell death. Since nicaraven has an inhibitory effect in PARS, as well as a radical scavenging effect, these results suggest that inhibition of hippocampal cell death caused by NMDA may be attributable to PARS inhibition by nicaraven.Key words: nicaraven, PARS inhibitor, radical scavenger, NMDA, hippocampus.
Protection from solar simulated radiation-induced DNA damage in cultured human fibroblasts by three commercially available sunscreens
Authors: Reinhardt Pascale , Cybulski Michelle , McNamee James P , McLean Jack R , Gorman Wayne , Deslauriers Yvon
Published: June 2003

Exposure to solar radiation can produce both acute and chronic changes in the skin, including sunburn, edema, immunosuppression, premature skin aging, and skin cancer. At the cellular level, solar radiation can produce adverse structural and functional changes in membrane proteins and lipids and in chromosomal and mitochondrial DNA. The increasing awareness of these adverse effects has led the public to demand better photoprotection. In this study, the alkaline comet assay was used to evaluate the photoprotective effects of three commercially available sunscreens at sun protection factors (SPF) 15 and 30. Human fibroblasts were used as target cells to conveniently study the effects of solar simulated radiation on DNA damage in the presence and absence of sunscreens. When human fibroblasts were exposed to various doses of solar simulated radiation, DNA damage, as measured in sunscreen-protected cells by the comet assay, was not significantly different from that detected in unexposed cells. At 1.0 and 1.5 minimal erythemal doses (MED), all sunscreens, at both SPF 15 and 30, provided nearly 100% photoprotection to the fibroblasts. Further studies are required to elucidate the role of UVA in the production and repair of DNA damage in cells exposed to sunlight.Key words: sunscreen, UVA, UVB, solar simulated radiation, comet assay.
Vascular responses to α-adrenergic stimulation and depolarization are enhanced in insulin-resistant and diabetic Psammomys obesus
Authors: Zoltowska M , St-Louis J , Ziv E , Sicotte B , Delvin E E , Levy E
Published: June 2003

Since vascular complications often accompany diabetes, we examined the influence of the endothelial lining on vascular reactivity in Psammomys obesus, a desert gerbil that acquires insulin resistance and diabetes when exposed to a laboratory diet. Vasoconstriction to phenylephrine and depolarizing KCl, as well as carbachol endothelium-dependent relaxation, were assessed in rings of thoracic aortae obtained from three groups: (i) group A, normoglycemicnormoinsulinemic; (ii) group B, normoglycemichyperinsulinemic, and (iii) group C, hyperglycemichyperinsulinemic animals. As expected, marked hypertriglyceridemia and hypercholesterolemia characterized groups B and C, which developed enhanced contractile responsiveness to phenylephrine and KCl compared with controls (group A). Furthermore, both experimental groups displayed a significant decrease in endothelium-dependent relaxation to carbachol. Altered lipid profiles are considered to play some role in the observed modification of aortic reactivity. Overall, our data indicate that vascular contractile responsiveness is enhanced early in the development of insulin resistance and diabetes in the female P. obesus.Key words: insulin resistance, diabetes, vascular reactivity, LDL-cholesterol, hypertriglyceridemia.
Effects and consequences of nerve injury on the electrical properties of sensory neurons
Authors: Abdulla Fuad A , Moran Timothy D , Balasubramanyan Sridhar , Smith Peter A
Published: June 2003

Nociceptive pain alerts the body to potential or actual tissue damage. By contrast, neuropathic or "noninflammatory" pain, which results from injury to the nervous system, serves no useful purpose. It typically continues for years after the original injury has healed. Sciatic nerve lesions can invoke chronic neuropathic pain that is accompanied by persistent, spontaneous activity in primary afferent fibers. This activity, which reflects changes in the properties and functional expression of Na+, K+, and Ca2+ channels, initiates a further increase in the excitability of second-order sensory neurons in the dorsal horn. This change persists for many weeks. The source of origin of the pain thus moves from the peripheral to the central nervous system. We hypothesize that this centralization of pain involves the inappropriate release of peptidergic neuromodulators from primary afferent fibers. Peptides such as substance P, neuropeptide Y (NPY), calcitonin-gene-related peptide (CGRP), and brain-derived neurotrophic factor (BDNF) may promote enduring changes in excitability as a consequence of neurotrophic actions on ion channel expression in the dorsal horn. Findings that form the basis of this hypothesis are reviewed. Study of the neurotrophic control of ion channel expression by spinal peptides may thus provide new insights into the etiology of neuropathic pain.Key words: neuropathic pain, spinal cord injury, allodynia, dorsal root ganglion, axotomy.
Bradykinin metabolism in rat hearts with left-ventricular hypertrophy following myocardial infarction
Authors: Dumoulin Marie-Josée , Adam Albert , Rouleau Jean-Lucien , Gosselin Hugues , Lamontagne Daniel
Published: June 2003

The aim of the present study was to assess the contribution of angiotensin I converting enzyme (ACE) and neutral endopeptidase (NEP) in the coronary degradation of bradykinin (BK) after left-ventricular hypertrophy following myocardial infarction (MI) in rats. Myocardial infarction was induced by left descendant coronary artery ligation, and the contribution of ACE and NEP in the degradation of exogenous BK after a single passage through the coronary bed was assessed at 2, 5, and 36 days post-MI. BK degradation rate (Vmax/Km) was found to be significantly lower in hearts at 36 days (3.30 ± 0.28 min1) compared with 2 days (4.39 ± 0.32 min1) for noninfarcted hearts, but this reduction was just above the statistical level of significance for post-MI hearts. In infarcted hearts, Vmax/Kmwas increased significantly 5 days post-MI (4.91 ± 0.28 min1) compared with the 2 and 36 day-groups (3.43 ± 0.20 and 2.78 ± 0.16 min1, respectively). The difference between noninfarcted and MI was significant only 2 days post-MI. Treatment with the vasopeptidase inhibitor, omapatrilat, showed that the relative contribution of ACE and NEP combined increased over time in infarcted hearts and became significantly higher 36 versus 2 days post-MI. Finally, the treatment with an ACE inhibitor (enalaprilat) and a NEP inhibitor (retrothiorphan) in the 36-day infarcted and noninfarcted hearts showed that the relative contribution of ACE in infarcted hearts was comparable with that of noninfarcted hearts, whereas the relative contribution of NEP was increased significantly in infarcted hearts. In conclusion, experimental MI in rats induces complex changes in the metabolism of exogenous BK. The changes resulted in an increased relative contribution of NEP 36 days after infarction.Key words: bradykinin, ACE, NEP, myocardial infarction.
Ethyl isopropyl amiloride inhibits smooth muscle cell proliferation and migration by inducing apoptosis and antagonizing urokinase plasminogen activator activity
Authors: Chen Yong-Xiang , O'Brien E R
Published: June 2003

Amiloride inhibits activation of the Na+H+exchanger (NHE), a critical step in smooth muscle cell (SMC) growth. While amiloride treatment reduces SMC proliferation and migration, as well as experimental lesion formation, these effects are not exclusively due to NHE inhibition and remain incompletely understood. The purpose of this study was to examine the mechanisms involved in amiloride-induced attenuation of SMC proliferation and migration, looking specifically at the potential role of apoptosis and urokinase plasminogen activator (uPA) activity in these processes. Rabbit SMCs in tissue culture were exposed to 1080μM of the amiloride analogue ethyl isopropyl amiloride (EIPA). Compared with controls, EIPA reduced DNA synthesis, cell number, and mitochondrial respiration, but without toxic effects on quiescent or proliferating cells. In a Boyden chamber assay, EIPA reduced uPA-induced SMC migration. Moreover, in a SMC scratch assay EIPA treatment resulted in a 66% reduction in the number of repopulating cells, a 92% decrease in the number of proliferating cells, and a 37-fold increase in the number of apoptotic cells. SMC apoptosis was frequently localized to the scratch edges, where cell proliferation and bcl-2 expression were absent. Finally, uPA enzymatic activity in the cell culture media was lower for EIPA-treated versus control SMCs. Therefore, EIPA inhibits both SMC proliferation and migration by inducing apoptosis and antagonizing uPA activity, respectively, and requires further study as an agent for reducing vascular lesion formation.Key words: smooth muscle cell, sodiumhydrogen exchanger, urokinase plasminogen activator, migration, apoptosis.
Effects of PACAP127 on the canine endocrine pancreas in vivo: interaction with cholinergic mechanism
Authors: Yamaguchi Nobuharu , Minassian Tamar Rita , Yamaguchi Sanae
Published: June 2003

The aim of the present study was to characterize the effects of pituitary adenylate cyclase activating polypeptide (PACAP) on the endocrine pancreas in anesthetized dogs. PACAP127 and a PACAP receptor (PAC1) blocker, PACAP627, were locally administered to the pancreas. PACAP127 (0.0055 μg) increased basal insulin and glucagon secretion in a dose-dependent manner. PACAP627 (200 μg) blocked the glucagon response to PACAP127 (0.5 μg) by about 80%, while the insulin response remained unchanged. With a higher dose of PACAP627 (500 μg), both responses to PACAP127 were inhibited by more than 80%. In the presence of atropine with an equivalent dose (128.2 μg) of PACAP627 (500 μg) on a molar basis, the insulin response to PACAP127 was diminished by about 20%, while the glucagon response was enhanced by about 80%. The PACAP127-induced increase in pancreatic venous blood flow was blocked by PACAP627 but not by atropine. The study suggests that the endocrine secretagogue effect of PACAP127 is primarily mediated by the PAC1 receptor, and that PACAP127 may interact with muscarinic receptor function in PACAP-induced insulin and glucagon secretion in the canine pancreas in vivo.Key words: atropine, PACAP, PAC1, muscarinic, interaction.
Serotonin effect on deiodinating activity in the rat
Authors: Sullo Alessio , Brizzi Guglielmo , Maffulli Nicola
Published: June 2003

Serotonin (5-HT) and thyroid hormones are part of a complex system modulating eating behaviour and energy expenditure. 5'-Deiodinase (5'-D) converts the relatively inactive thyroxine (T4) to triiodothyronine (T3), and its activity is an indirect measure of T3 production in peripheral tissues, particularly in the brain, intrascapular brown adipose tissue (IBAT), heart, liver, and kidney. We evaluated the effect of 5-HT on 5'-D activity during basal conditions and after short (30 min) cold exposure (thyroid stimulating hormone stimulation test, TST). 5'-D activity was assessed in the liver, heart, brain, kidney, and IBAT. TST increases 5'-D activity in the brain, heart, and IBAT and decreases it in kidney, leaving it unchanged in the liver. 5-HT alone did not modify 5'-D activity in the organs under study but decreased it in the IBAT, heart, and brain when injected before the TST was administered. Our results confirm the important role of 5-HT in thermoregulation, given its peripheral site of action, in modulating heat production controlling intracellular T3 production. These effects are more evident when heat production is upregulated during cold exposure in organs containing type II 5'-D, such as the brain, heart, and IBAT, which are able to modify their function during conditions that alter energy balance. In conclusion, 5-HT may also act peripherally directly on the thyroid and organs containing type II 5'-D, thus controlling energy expenditure through heat production.Key words: serotonin, deiodinase activity, thyroid hormone, brown adipose tissue, thermogenesis, rat organs.
Chronic carbon monoxide exposure of hypoxic rats increases in vitro sensitivity of pulmonary artery smooth muscle
Authors: Dubuis Eric , Gautier Mathieu , Melin Alexandre , Rebocho Manuel , Girardin Catherine , Bonnet Pierre , Vandier Christophe
Published: June 2003

Exogenous carbon monoxide (CO) induces pulmonary vasodilation by acting directly on pulmonary artery (PA) smooth muscle cells. We investigated the contribution of K+ channels and soluble guanylyl cyclase to the regulation of PA tone by acute CO in chronic hypoxic rats (3 weeks at 0.5 atm (1 atm = 101.325 kPa); hypoxic) and in chronic hypoxic rats exposed to exogenous CO (3 weeks at 0.5 atm + 50 ppm CO; hypoxic-CO). Acute CO induced relaxation in PA rings from all animals. However, the amplitude of CO relaxation was significantly decreased in hypoxic rings and increased in hypoxic-CO rings. This different effect occurred with a decrease and an increase of pD2, respectively, in hypoxic and hypoxic-CO rings. We showed a positive relation between the percentage of inhibition of CO relaxation by a blocker of K+ channels and the increase of CO sensitivity. Thus, we showed for the first time that chronic hypoxia decreases acute CO sensitivity, which in contrast, increases in the presence of chronic CO. The present study provides initial evidence of a link between increased K+-channel activity and CO sensitivity.Key words: K+-channel blocker, tetraethylammonium, soluble guanylyl cyclase, gasotransmitter.
STOCHASTIC ANALYSIS OF THE ZIGZAG MAP
Authors: VAN WYK MICHAËL A. , STEEB WILLI-HANS
Published: June 2003

We present a stability and stochastic analysis of the zigzag map which describes the dynamical behavior of an electrical switching circuit. Analytical expressions are derived for the invariant density and the corresponding Lyapunov exponent for specific parameter values.
SUPPORT VECTOR IDENTIFICATION OF SEISMIC ELECTRIC SIGNALS
Authors: IFANTIS A. , PAPADIMITRIOU S.
Published: June 2003

Traditional pattern recognition approaches usually generalize poorly on difficult tasks as the problem of identification of the Seismic Electric Signals (SES) electrotelluric precursors for earthquake prediction. This work demonstrates that the Support Vector Machine (SVM) can perform well on this application. The a priori knowledge consists of a set of VAN rules for SES signal detection. The SVM extracts implicitly these rules from properly preprocessed features and obtains generalization performance founded upon a robust mathematical basis. The potentiality of obtaining generalization potential even in feature spaces of high dimensionality bypasses the problems due to overtraining of the conventional machine learning architectures. The paper considers the optimization of the generalization performance of the SVM. The results indicate that the SVM outperforms many alternative computational intelligence models for the task of SES pattern recognition.
APPLYING FEATURE TRACKING TO PARTICLE IMAGE VELOCIMETRY
Authors: CHETVERIKOV DMITRY
Published: June 2003

Particle Image Velocimetry (PIV) is a popular approach to flow visualization and measurement in hydro- and aerodynamic studies and applications. The fluid is seeded with particles that follow the flow and make it visible. Traditionally, correlation techniques have been used to estimate the displacements of the particles in a digital PIV sequence. These techniques are relatively time-consuming and noise-sensitive. Recently, an optical flow estimation technique developed in machine vision has been successfully used in Particle Image Velocimetry. Feature tracking is an alternative approach to motion estimation, whose application to PIV is proposed and studied in this paper. Two efficient feature tracking algorithms are customized and applied to PIV. The algorithmic solutions of the application are described. In particular, techniques for coherence filtering and interpolation of a velocity field are developed. To assess the proposed and the previous approaches, velocity fields obtained by the different methods are quantitatively compared for numerous synthetic and real PIV sequences. It is concluded that the tracking algorithms offer Particle Image Velocimetry a good alternative to both correlation and optical flow techniques.
THE EFFECTS OF QUANTIZATION ON MULTI-LAYER FEEDFORWARD NEURAL NETWORKS
Authors: JIANG MINGHU , GIELEN GEORGES
Published: June 2003

In this paper we investigate the combined effect of quantization and clipping on multi-layer feedforward neural networks (MLFNN). Statistical models are used to analyze the effects of quantization in a digital implementation. We analyze the performance degradation caused as a function of the number of fixed-point and floating-point quantization bits in the MLFNN. To analyze a true nonlinear neuron, we adopt the uniform and normal probability distributions, compare the training performances with and without weight clipping, and derive in detail the effect of the quantization error on forward and backward propagation. No matter what distribution the initial weights comply with, the weights distribution will approximate a normal distribution for the training of floating-point or high-precision fixed-point quantization. Only when the number of quantization bits is very low, the weights distribution may cluster to ± 1 for the training with fixed-point quantization. We establish and analyze the relationships for a true nonlinear neuron between inputs and outputs bit resolution, the number of network layers and the performance degradation, based on statistical models of on-chip and off-chip training. Our experimental simulation results verify the presented theoretical analysis.
CLASSIFICATION OF RESPIRATORY SOUNDS BY USING AN ARTIFICIAL NEURAL NETWORK
Authors: DOKUR ZÜMRAY , ÖLMEZ TAMER
Published: June 2003

In this paper, a classification method for respiratory sounds (RSs) in patients with asthma and in healthy subjects is presented.

Wavelet transform is applied to a window containing 256 samples. Elements of the feature vectors are obtained from the wavelet coefficients. The best feature elements are selected by using dynamic programming. Grow and Learn (GAL) neural network, Kohonen network and multi-layer perceptron (MLP) are used for the classification.

It is observed that RSs of patients (with asthma) and healthy subjects are successfully classified by the GAL network.
AN INTEGRATED SYSTEM FOR HANDWRITTEN DOCUMENT IMAGE PROCESSING
Authors: KAVALLIERATOU E. , DROMAZOU N. , FAKOTAKIS N. , KOKKINAKIS G.
Published: June 2003

In this paper we attempt to face common problems of handwritten documents such as nonparallel text lines in a page, hill and dale writing, slanted and connected characters. Towards this end an integrated system for document image preprocessing is presented. This system consists of the following modules: skew angle estimation and correction, line and word segmentation, slope and slant correction. The skew angle correction, slope correction and slant removing algorithms are based on a novel method that is a combination of the projection profile technique and the Wigner–Ville distribution. Furthermore, the skew angle correction algorithm can cope with pages whose text line skew angles vary, and handle them by areas. Our system can be used as a preprocessing stage to any handwriting character recognition or segmentation system as well as to any writer identification system. It was tested in a wide variety of handwritten document images of unconstrained English and Modern Greek text from about 100 writers. Additionally, combinations of the above algorithms have been used in the framework of the ACCeSS system (European project LE-1 1802, aiming at the automatic processing of application forms of insurance companies) as well as in the processing of GRUHD and IAM-B databases for automating the procedure of extracting data.
SHAPE UNDERSTANDING SYSTEM: THE VISUAL REASONING PROCESS
Authors: LES ZBIGNIEW , LES MAGDALENA
Published: June 2003

In this paper the visual reasoning that is part of visual thinking capabilities of the shape understanding system (SUS) is investigated. This research is a continuation of the authors' previous work focused on investigating understanding capabilities of the intelligent systems based on the shape understanding system. SUS is an example of the visual understanding system, where sensory information is transformed into the multilevel representation in the concept formation process that is part of the visual thinking capabilities. The visual reasoning involves transformation of the description of the object when passing consequent stages of the reasoning process and the reasoning and processing of the data are mutually dependent.
ACTIVE HEAD TRACKING BASED ON CHROMATIC SHAPE FITTING
Authors: ZHANG JASON Z. , WU Q. M. JONATHAN , GRUVER WILLIAM A.
Published: June 2003

This paper presents a method for tracking a human head based on the integration of camera saccade and chromatic shape fitting, which are implemented as functional modules in an active tracking system. Head motion is detected in the saccade module by extracting edges from two successive images. The position of the head in the current image is approximated as the centroid of the apparition formed by the moving edges of the target. A visual position cue is used to drive a pan/tilt camera to perform real-time saccade keeping the target in the foveal area in the image. The shape-fitting module is invoked to extract more information from the target. The shape of the target is modeled as an ellipse whose position, orientation and size are dynamically determined by shape fitting, and implemented with a color registration technique. In the proposed method, quasi real-time pursuit is achieved using a Pentium II computer in an uncontrolled environment with arbitrary relative motion between the target and camera.
SEGMENTATION OF BOVINE LIVESTOCK IMAGES USING GA AND ASM IN A TWO-STEP APPROACH
Authors: VELASCO HORACIO MANUEL GONZÁLEZ , ORELLANA CARLOS JAVIER GARCÍA , ALIGUÉ FRANCISCO JAVIER LÓPEZ , MACÍAS MIGUEL MACÍAS , CABALLERO RAMÓN GALLARDO
Published: June 2003

In this work a system based on genetic algorithms (GA) and active shape models (ASM) is presented that, in a two-step approach, is able to accurately find a particular object within the image. The aim of the first stage is to approximately locate the object in order to serve as an initialization for the second. Following a method similar to that used by other authors, a model of the desired shape (cows in lateral position) is constructed using PDM, and later the search within the image is carried out based on instances of that model, and using genetic algorithm techniques, for which several objective functions are suggested. In the second stage we attempt to make a fine adjustment of our instance to the object in the image, starting from the result of the previous process. Consequently, we propose two different techniques compared afterwards: deformable contours (specifically active shape models) and a restricted genetic search. Finally, the system is tested over a database of 309 animal images, and results are presented.
CLUSTER SYNCHRONIZATION IN THREE-DIMENSIONAL LATTICES OF DIFFUSIVELY COUPLED OSCILLATORS
Authors: BELYKH VLADIMIR N. , BELYKH IGOR V. , HASLER MARTIN , NEVIDIN KONSTANTIN V.
Published: June 2003

Cluster synchronization modes of continuous time oscillators that are diffusively coupled in a three-dimensional (3-D) lattice are studied in the paper via the corresponding linear invariant manifolds. Depending in an essential way on the number of oscillators composing the lattice in three volume directions, the set of possible regimes of spatiotemporal synchronization is examined. Sufficient conditions of the stability of cluster synchronization are obtained analytically for a wide class of coupled dynamical systems with complicated individual behavior. Dependence of the necessary coupling strengths for the onset of global synchronization on the number of oscillators in each lattice direction is discussed and an approximative formula is proposed. The appearance and order of stabilization of the cluster synchronization modes with increasing coupling between the oscillators are revealed for 2-D and 3-D lattices of coupled Lur'e systems and of coupled Rössler oscillators.
ON SPATIAL PERIODIC ORBITS AND SPATIAL CHAOS
Authors: CHEN GUANRONG , LIU SHU TANG
Published: June 2003

This paper introduces an analytical method for constructing spatial periodic orbits of specified periods. This result is then extended to generating spatial chaos in the sense of Li and Yorke.
DEFORMATION OF TRAVELING WAVES IN DELAYED CELLULAR NEURAL NETWORKS
Authors: WENG PEIXUAN , WU JIANHONG
Published: June 2003

In this paper, we establish the existence and describe the global structure of traveling waves for a class of lattice delay differential equations describing cellular neural networks with distributed delayed signal transmission. We describe the transition of wave profiles from monotonicity, damped oscillation, periodicity, unboundedness and back to monotonicity as the wave speed is varied. We also describe an interval of the wave speed where the structure of the wave solution is unknown since the corresponding profile equation involves distributed argument of both advanced and retarded types, and we present some preliminary numerical simulation to illustrate the complexity.
RESCALED EVOLUTION SETS OF LINEAR CELLULAR AUTOMATA ON A CYLINDER
Authors: BARBÉ A. , HAESELER F. V. , PEITGEN H.-O. , SKORDEV G.
Published: June 2003

Rescaled evolution sets of linear cellular automata on a lattice ℤ ⊕ G, where G is a finite Abelian group, with states in the finite field [Formula: see text] are defined and investigated.
STICK-SLIP DYNAMICS OF A TWO-DEGREE-OF-FREEDOM SYSTEM
Authors: AWREJCEWICZ J. , OLEJNIK P.
Published: June 2003

Two-degree-of-freedom autonomous system with friction is analyzed numerically. The friction coefficient has been smoothened using arc tan function. The standard, but slightly modified chaos identification tools have been applied for the analyzed discontinuous system. Some interesting examples of stick-slip regular and chaotic dynamics have been illustrated and discussed.
LOCAL FEEDBACK CONTROL OF THE NEIMARK–SACKER BIFURCATION
Authors: YAGHOOBI HASSAN , ABED EYAD H.
Published: June 2003

Local bifurcation control designs have been addressed in the literature for stationary, Hopf, and period doubling bifurcations. This paper addresses the local feedback control of the Neimark–Sacker bifurcation, in which an invariant closed curve emerges from a nominal fixed point of a discrete-time system as a parameter is slowly varied. The analysis of this bifurcation is more involved than for previously considered bifurcations. The paper develops the stability and amplitude equations for the bifurcated invariant curves of the Neimark–Sacker bifurcation, and then proceeds to apply these relationships in the design of nonlinear feedbacks. The feedback controllers are applied to two examples: the delayed logistic map and a model reference adaptive control system model.
COMPOSITE SLIDING MODE CONTROL OF CHAOTIC SYSTEMS WITH UNCERTAINTIES
Authors: WANG CHUN-CHIEH , SU JUHNG-PERNG
Published: June 2003

This paper presents a new approach to the design of a composite sliding mode control for a class of chaotic systems with uncertainties. A significant feature of this control scheme is the incorporation of a new complementary sliding variable to the conventional sliding variable in order that a high-performance controller can be obtained. It has been shown that the guaranteed steady-state error bounds are reduced by half, as compared with the conventional sliding control. Moreover, the dynamic responses during the reaching phase are also significantly improved. We used a controlled uncertain Lorenz system and a controlled uncertain Chua's circuit as illustrative examples to demonstrate the effectiveness of the design.
ADAPTIVE IDENTIFICATION ALGORITHMS FOR AR SYSTEM DRIVEN BY CHAOTIC SEQUENCE
Authors: WANG BAO-YUN , CHOW T. W. S. , NG K. T.
Published: June 2003

In this article the identification of AR system driven by chaotic sequences is addressed. This problem emerges in chaotic communication system, in which chaos-modulated signal passes through a channel described as an AR system. Two adaptive algorithms are presented to tackle this problem. Compared with the existing algorithms such as MPSV and MNPE, the proposed algorithms have very low computational complexities and can be used to track the system parameters in a slowly time-variant environment. The obtained simulation results illustrate that the proposed scheme can offer a better estimation accuracy than the conventional typical method in the high SNR case.
ON THE INTEGRABILITY OF QUASIHOMOGENEOUS AND RELATED PLANAR VECTOR FIELDS
Authors: GARCÍA ISAAC A.
Published: June 2003

In this work we consider planar quasihomogeneous vector fields and we show, among other qualitative properties, how to calculate all the inverse integrating factors of such C1 systems. Additionally, we obtain a necessary condition in order to have analytic inverse integrating factors and first integrals for planar positively semi-quasihomogeneous vector fields which are related to the existence of polynomial inverse integrating factors and first integrals for the quasihomogeneous cut. Examples are given and their relationship with Kovalevskaya exponents is shown.
QUASIPERIODIC SOLUTIONS AND CHAOS IN A PERIODICALLY FORCED PREDATOR–PREY MODEL WITH AGE STRUCTURE FOR PREDATOR
Authors: TANG SANYI , CHEN LANSUN
Published: June 2003

We subject the classical Volterra predator–prey ecosystem model with age structure for predator to periodic forcing, which in its unforced state has a globally stable focus as its equilibrium. The periodic forcing is affected by assuming a periodic variation in the intrinsic growth rate of prey. By using the Poincaré surface-of-section technique and numerical experiments, an abundance of periodic solutions, quasiperiodic solutions and chaotic solutions are revealed. The route of transitions to chaos were found to be very complex which include quasiperiodicity and frequency locking.
ANALYSIS OF APERIODIC OSCILLATIONS IN A FLOW MODEL OF A SWITCHING SYSTEM
Authors: TANAKA HIROTO , USHIO TOSHIMITSU
Published: June 2003

In this paper, we consider a switching system modeled by a discrete-time flow model, which has piecewise linear dynamics. In the system, it has been known that aperiodic oscillations occur. We qualitatively classify behaviors of the system into three modes, and define "blocks" consisting of the modes. We define a kind of Poincaré map by using the blocks, and show that the system has an invariant region in the Poincaré map. Moreover, we show that the Poincaré map can be reduced to a one-dimensional map. Finally, applying Lasota–Yorke's theorem to the one-dimensional map, we prove that the aperiodic oscillation is chaotic.
LIMITER CONTROL OF A CHAOTIC RF TRANSISTOR OSCILLATOR
Authors: CORRON NED J. , HOPPER BUCKLEY A. , PETHEL SHAWN D.
Published: June 2003

We report experimental control of chaos in an electronic circuit at 43.9 MHz, which is the fastest chaos control reported in the literature to date. Limiter control is used to stabilize a periodic orbit in a tuned collector transistor oscillator modified to exhibit simply folded band chaos. The limiter is implemented using a transistor to enable monitoring the relative magnitude of the control perturbation. A plot of the relative control magnitude versus limiter level shows a local minimum at period-1 control, thereby providing strong evidence that the controlled state is an unstable periodic orbit (UPO) of the uncontrolled system.
PIECEWISE LINEAR FEEDBACK SYSTEMS WITH ARBITRARY NUMBER OF LIMIT CYCLES
Authors: LLIBRE JAUME , PONCE ENRIQUE
Published: June 2003

Given an arbitrary positive integer n, it is shown that there exist planar piecewise linear differential systems with at least n limit cycles.
APPROXIMATION OF THE FRACTAL TRANSITION USING ATTRACTORS EXCITED BY PERIODIC INPUTS
Authors: OKA HISAKI , GOHARA KAZUTOSHI
Published: June 2003

Dissipative continuous dynamical systems with multiple external inputs are studied. When inputs are stochastically switched, the dynamics is characterized by trajectories with attractive fractal-like structures. We call this dynamics the fractal transition. This paper shows that a set of attractors obtained by periodic inputs can approximate trajectories of the fractal transition that have equal switching probabilities. The Hausdorff distance D is used to estimate the accuracy of approximation. We also present two numerical experiments, using harmonic and Duffing oscillators, corresponding to linear and nonlinear systems, respectively. We numerically show that D ≃ 0 given a large enough number of periodic inputs. For linear systems, under some conditions, we analytically derive the upper bound of D and show that D converges to 0.
LOCAL BIFURCATION CONTROL IN A ROTOR-MAGNETIC BEARING SYSTEM
Authors: JI J. C. , HANSEN COLIN H.
Published: June 2003

Linear-plus-nonlinear feedback control is used to stabilize Hopf bifurcation in a rotor-magnetic bearing system, for which the linearized system possesses a double zero eigenvalues. The addition of nonlinear (quadratic) terms to the original linear feedback control formulation is used to modify the coefficients of the nonlinear terms in the reduced normal forms. It is found that feedback control incorporating certain quadratic terms renders the Hopf bifurcation supercritical. Finally, illustrative examples are given to verify the analytical results.
OBSERVER BASED CHAOTIC MESSAGE TRANSMISSION
Authors: MORGÜL ÖMER , SOLAK ERCAN , AKGÜL MURAT
Published: June 2003

We consider observer based synchronization of continuous-time chaotic systems. We present two message transmission schemes for such systems. The first one is based on chaotic masking and modulation, and the second one is based on only chaotic modulation. We show that in these schemes, the message may be recovered under certain conditions. We show that the proposed schemes are robust with respect to noise and parameter mismatch. We also present some simulation results.
BIFURCATION OF EQUILIBRIUM IN MICROMACHINED ELASTIC STRUCTURES WITH LIQUID INTERFACE
Authors: WANG P. K. C.
Published: June 2003

The determination of bifurcation of equilibrium in micromachined elastic structures with liquid interface is posed as nonlinear boundary-value problems associated with spatially distributed models involving fluid forces. Explicit nonlinear algebraic equations for determining the bifurcation points associated with micromachined cantilever beam and membrane are derived. These equations permit bifurcation analysis involving any system parameter. It is shown that bifurcation of equilibrium in these structures is of the fold type. Numerical results are obtained for typical cantilever beam and membrane.
ABOUT A NEW CLASS OF INVARIANT AREAS GENERATED BY TWO-DIMENSIONAL ENDOMORPHISMS
Authors: CATHALA J. C.
Published: June 2003

Invariant areas generated by two-dimensional endomorphisms are studied using the method of critical curves. The invariant areas considered in this paper are obtained by iterating the noninvariant set constituted by the connected basin of an attracting set or the immediate basin of a nonconnected basin. This new kind of invariant area is of mixed type in the sense that its boundary is made up of critical curves arcs and arcs of saddle manifolds. The presentation is illustrated by three examples. A bifurcation changing the degree of connexity of an invariant area is described.
SYNCHRONIZATION OF COUPLED EXTENDED DYNAMICAL SYSTEMS: A SHORT REVIEW
Authors: ZANETTE DAMIÁN H. , MORELLI LUIS G.
Published: June 2003

We briefly review the synchronization properties of cross-coupled spatially extended dynamical systems, with particular emphasis on elementary cellular automata and Kauffman networks subject to stochastic coupling. We also discuss the main results for the joint evolution of deterministically cross-coupled Ginzburg–Landau equations and neural networks. Both numerical and analytical approaches are addressed, and the main differences with the synchronization of zero-dimensional systems are highlighted. New results are presented characterizing the critical behavior at the synchronization transition of coupled Kauffman networks.
Monetary Sterilization of Capital Inflows through the Central-Provident-Fund Savings in Singapore
Authors: Wu Ying , Wang Ruifang
Published: June 2003

This paper examines the monetary sterilization mechanism of the Singapore economy. We argue that, in the absence of a well-developed open financial market, the Central Provident Fund (CPF) has in fact played a role as a quasi-market mechanism in sterilizing the effect of foreign-exchange assets inflow. Using the error-correction-mechanism (ECM) approach, we model the implicit monetary sterilization mechanism and estimate the offset coefficient between the net-domestic-credit component and the net-foreign-asset component of the monetary base. The estimated ECM regression coefficient suggests that monetary sterilization in Singapore is nearly perfect for the 1984–1995 period. The estimates of other macroeconomic relations also support the hypothesis of the quasi-market monetary sterilization mechanism.
Credit Evaluation for Small and Medium-sized Enterprises by the Examination of Firm-specific Financial Ratios and Non-financial Variables: Evidence from Taiwan
Authors: Kuo Hsien-Chang , Wang Lie-Huey , Sheu Her-Jiun , Li Fa-Kuang
Published: June 2003

A credit evaluation model for SMEs in Taiwan based on the characteristics of financial as well as non-financial data is proposed in this paper. While most financial distress prediction models use financial ratios as predictive variables, this study also integrates non-financial data as predictive variables. Kuo and Li (1999) proposed that certain firm-specific financial ratios have informational content. Moreover, the introduction of non-financial variables does enhance the model's discrimination power. The proposed credit evaluation model makes it easier to classify successful or failed SMEs.
Sequential Capital Budgeting as Real Options: The Case of a New DRAM Chipmaker in Taiwan
Authors: Duan Chang-Wen , Lin William T. , Lee Cheng Few
Published: June 2003

We evaluate the initial public offering price of a new DRAM chipmaker in Taiwan in accordance with the compound real call options model of Lin (2002). The worldwide average sales price is the underlying variable, and the average production cost of the new DRAM foundry is the exercise price. The twin security is defined as a portfolio of DRAM manufacturing firms publicly listed in Taiwan stock markets. We estimate the dividend-like yield with two methods, and find that the yield is negative. The negative dividend-like yield results from the negative correlation between the newly constructed DRAM foundry and its twin security, implying the diversification advantage of a new generation of DRAM foundry with a relative low cost of investment opportunity. We solve the critical value for the multivariate normal integral with the secant method, approximating the integral with the lattice method. It has been found that there is only a 4.6% difference between the market IPO price and the estimated one.
The Role of Non-Bank Financial Intermediaries in Propagating Korea's Financial Crisis
Authors: Miles William
Published: June 2003

The Korean crisis has been analyzed for the causal role banks played through the "credit view". Non-bank lenders have grown more important than banks in providing loans, but their role in creating financial instability has been ignored. This paper fills this gap, and demonstrates that non-banks were an important source of dislocation. Moreover, these results offer a counter-argument to proposals for "narrow banking". Narrow banking would separate deposit taking and lending into two enterprises, hopefully reducing vulnerability to panics. The poor performance of non-bank lenders even relative to banks in the Korean episode casts doubt on this model.
Valuation of Covered Warrant Subject to Default Risk
Authors: Chen Shen-Yuan
Published: June 2003

There is no margin settlement mechanism for existing covered warrants in Taiwan, thus the credit risk of the warrant issuer must be considered when investors evaluate the price of a covered warrant. This paper applies the vulnerable option valuation model to empirically study the difference in the theoretical value of a vulnerable warrant, Black–Scholes option price and the market price of warrant by using the Taiwan warrant data. Empirical results show that the theoretical value of a vulnerable warrant is lower than the Black–Scholes non-vulnerable option value and its market value.
A TRUE ANNEALING APPROACH TO THE MARRIAGE IN HONEY-BEES OPTIMIZATION ALGORITHM
Authors: TEO JASON , ABBASS HUSSEIN A.
Published: June 2003

Marriage in Honey-Bees Optimization is a new swarm intelligence technique inspired by the marriage process of honey-bees. It has been shown to be very effective in solving the propositional satisfiability problem known as 3-SAT. The objective of this paper is to test a conventional annealing approach as the basis for determining the pool of drones. The modified algorithm is tested using a group of randomly generated hard 3-SAT problems to compare its behavior and efficiency against previous implementations. The overall performance of the MBO algorithm was found to have improved significantly using the proposed annealing function. Furthermore, a dramatic improvement was noted with the committee machine using this true annealing approach.
K‐theory for Cuntz‐Krieger algebras arising from real quadratic maps
Authors: Martins Nuno , Severino Ricardo , Ramos J. Sousa
Published: June 2003

We compute the K‐groups for the Cuntz‐Krieger algebras , where is the Markov transition matrix arising from the kneading sequence
𝒦(fμ) of the one‐parameter family
of real quadratic maps fμ.
Fixed‐point iteration processes for non‐Lipschitzian mappings ofasymptotically quasi‐nonexpansive type
Authors: Sahu Daya Ram , Jung Jong Soo
Published: June 2003

We study convergences of Mann and Ishikawa iteration processes for
mappings of asymptotically quasi‐nonexpansive type in Banach spaces.