bluuebunny/crossref_metadata_2025 huggingface dataset:
Role for Periodontitis in the Progression of Lipid Deposition in an Animal Model
Authors: Jain Ashish , Batista Eraldo L. , Serhan Charles , Stahl Gregory L. , Van Dyke Thomas E.
Published: September 2003

Epidemiologic studies have implicated periodontitis as a risk factor for the development of cardiovascular disease. However, no prospective studies investigating this potential relationship have been carried out. Age- and sex-matched New Zealand White rabbits were maintained on a diet consisting of 0.5% fat for 13 weeks to induce the accumulation of lipid deposits in the aorta as a model for atherogenesis. One-half of the animals received silk ligatures around their mandibular premolars followed by an application of a periodontal pathogen,
Porphyromonas gingivalis
, to induce periodontitis. Animals were sacrificed after 14 weeks. Periodontal disease severity was quantified radiographically, histologically, and by direct visualization of bone loss on defleshed skulls. Lipid deposition was evaluated by computer-assisted morphometry in the aortas en face after lipid deposits were stained with Sudan IV. Animals with experimentally induced periodontitis had more extensive accumulations of lipids in the aorta than did nonperiodontitis animals (
P
< 0.05), and there was a positive correlation between the severity of periodontal disease and the extent of lipid deposition (
r
2
= 0.9501). The results provide direct evidence that periodontitis may be a risk factor and may contribute to the pathogenesis of atherosclerosis. The data support the concept that infections at remote locations can modulate atherosclerotic events distantly.
Streptococcus pyogenesInfection Induces Septic Arthritis with Increased Production of the Receptor Activator of the NF-κB Ligand
Authors: Sakurai Atsuo , Okahashi Nobuo , Nakagawa Ichiro , Kawabata Shigetada , Amano Atsuo , Ooshima Takashi , Hamada Shigeyuki
Published: September 2003

Bacterial arthritis is a rapidly progressive and highly destructive joint disease in humans, withStaphylococcus aureusandNeisseria gonorrhoeaethe major causative agents, although beta-hemolytic streptococci as well often induce the disease. We demonstrate here that intravenous inoculation of CD-1 mice with the group A streptococcus (GAS) speciesStreptococcus pyogenesresulted in a high incidence of septic arthritis. Signs of arthritis emerged within the first few days after injection, and bacterial examinations revealed that colonization of the inoculated GAS in the arthritic joints persisted for 21 days. Induction of persistent septic arthritis was dependent on the number of microorganisms inoculated. Immunohistochemical staining of GAS with anti-GAS antibodies revealed colonization in the joints of infected mice. Cytokine levels were quantified in the joints and sera of infected mice by using an enzyme-linked immunosorbent assay. High levels of interleukin-1β (IL-1β) and IL-6 were detected in the joints from 3 to 20 days after infection. We noted that an increase in the amount of receptor activator of NF-κB ligand (RANKL), which is a key cytokine in osteoclastogenesis, was also evident in the joints of the infected mice. RANKL was not detected in sera, indicating local production of RANKL in the infected joints. Blocking of RANKL by osteoprotegerin, a decoy receptor of RANKL, prevented bone destruction in the infected joints. These results suggest that GAS can colonize in the joints and induce bacterial arthritis. Local RANKL production in the infected joints may be involved in bone destruction.
Expression of
Cpgp40/15
in
Toxoplasma gondii
: a Surrogate System for the Study of
Cryptosporidium
Glycoprotein Antigens
Authors: O'Connor R. M. , Kim K. , Khan F. , Ward H. D.
Published: September 2003

Cryptosporidium parvum
is a waterborne enteric coccidian that causes diarrheal disease in a wide range of hosts. Development of successful therapies is hampered by the inability to culture the parasite and the lack of a transfection system for genetic manipulation. The glycoprotein products of the
Cpgp40/15
gene, gp40 and gp15, are involved in
C. parvum
sporozoite attachment to and invasion of host cells and, as such, may be good targets for anticryptosporidial therapies. However, the function of these antigens appears to be dependent on the presence of multiple O-linked α-
N
-acetylgalactosamine (α-GalNAc) determinants. A eukaryotic expression system that would produce proteins bearing glycosylation patterns similar to those found on the native
C. parvum
glycoproteins would greatly facilitate the molecular and functional characterization of these antigens. As a unique approach to this problem, the
Cpgp40/15
gene was transiently expressed in
Toxoplasma gondii
, and the expressed recombinant glycoproteins were characterized. Antisera to gp40 and gp15 reacted with the surface membranes of tachyzoites expressing the
Cpgp40/15
construct, and this reactivity colocalized with that of antiserum to the
T. gondii
surface protein SAG1. Surface membrane localization was dependent on the presence of the glycophosphatidylinositol anchor attachment site present in the gp15 coding sequence. The presence of terminal O-linked α-GalNAc determinants on the
T. gondii
recombinant gp40 was confirmed by reactivity with
Helix pomatia
lectin and the monoclonal antibody 4E9, which recognizes α-GalNAc residues, and digestion with α-
N
-acetylgalactosaminidase. In addition to appropriate localization and glycosylation,
T. gondii
apparently processes the gp40/15 precursor into the gp40 and gp15 component glycopolypeptides, albeit inefficiently. These results suggest that a surrogate system using
T. gondii
for the study of
Cryptosporidium
biology may be useful.
Effector ExoU from the Type III Secretion System Is an Important Modulator of Gene Expression in Lung Epithelial Cells in Response to
Pseudomonas aeruginosa
Infection
Authors: McMorran B. , Town L. , Costelloe E. , Palmer J. , Engel J. , Hume D. , Wainwright B.
Published: September 2003

Pseudomonas aeruginosa
is an important pathogen in immunocompromised patients and secretes a diverse set of virulence factors that aid colonization and influence host cell defenses. An important early step in the establishment of infection is the production of type III-secreted effectors translocated into host cells by the bacteria. We used cDNA microarrays to compare the transcriptomic response of lung epithelial cells to
P. aeruginosa
mutants defective in type IV pili, the type III secretion apparatus, or in the production of specific type III-secreted effectors. Of the 18,000 cDNA clones analyzed, 55 were induced or repressed after 4 h of infection and could be classified into four different expression patterns. These include (i) host genes that are induced or repressed in a type III secretion-independent manner (32 clones), (ii) host genes induced specifically by ExoU (20 clones), and (iii) host genes induced in an ExoU-independent but type III secretion dependent manner (3 clones). In particular, ExoU was essential for the expression of immediate-early response genes, including the transcription factor c-Fos. ExoU-dependent gene expression was mediated in part by early and transient activation of the AP1 transcription factor complex. In conclusion, the present study provides a detailed insight into the response of epithelial cells to infection and indicates the significant role played by the type III virulence mechanism in the initial host response.
Interleukin-15 as an Immune Adjuvant To Increase the Efficacy of
Mycobacterium bovis
Bacillus Calmette-Guérin Vaccination
Authors: Umemura Masayuki , Nishimura Hitoshi , Saito Kimika , Yajima Toshiki , Matsuzaki Goro , Mizuno Satoru , Sugawara Isamu , Yoshikai Yasunobu
Published: September 2003

Interleukin-15 (IL-15) transgenic mice which had been inoculated with
Mycobacterium bovis
bacillus Calmette-Guérin (BCG) 24 weeks previously showed resistance against airborne infection with
Mycobacterium tuberculosis
H37Rv accompanied by an increased CD8
+
-Tc1-cell response. IL-15 may be used as an immune adjuvant given with BCG vaccination to enhance its biologic efficacy.
The Type IVB Pili of
Salmonella enterica
Serovar Typhi Bind to the Cystic Fibrosis Transmembrane Conductance Regulator
Authors: Tsui Inez S. M. , Yip Cecilia M. C. , Hackett Jim , Morris Christina
Published: September 2003

Salmonella enterica
serovar Typhi expresses type IVB pili. We show that the prePilS protein (the soluble precursor form of the structural pilin) interacts with a 15-mer peptide representing the first extracellular domain of the cystic fibrosis transmembrane conductance regulator (CFTR), a recognized human epithelial cell receptor for serovar Typhi (G. B. Pier et al., Nature 393:79-82, 1998). This indicates that after mediating bacterial self-association (C. Morris et al., Infect. Immun. 71:1141-1146, 2003), the pili then act to attach the bacterial clumps to CFTR in the membrane of gut epithelial cells. These sequential type IVB pilus-mediated events cannot be performed by (for example)
S. enterica
serovar Typhimurium, which may explain why only serovar Typhi causes epidemics of enteric fever in humans.
Inflammatory Cytokine Production Predominates in Early Lyme Disease in Patients with Erythema Migrans
Authors: Glickstein Lisa , Moore Brian , Bledsoe Tara , Damle Nitin , Sikand Vijay , Steere Allen C.
Published: September 2003

In a study of cytokine production ex vivo by
Borrelia burgdorferi
-stimulated peripheral blood mononuclear cells from 27 patients with culture-positive erythema migrans, production of inflammatory cytokines predominated, particularly gamma interferon and, to a lesser degree, tumor necrosis factor alpha. In contrast, with the exception of interleukin-13, anti-inflammatory cytokine production was negligible. Thus,
B. burgdorferi
antigens in early Lyme disease often induce a strong inflammatory response.
Antibody Responses Elicited against theTreponema pallidumRepeat Proteins Differ during Infection with Different Isolates ofTreponema pallidumsubsp.pallidum
Authors: Leader Brandon T. , Hevner Karin , Molini Barbara J. , Barrett Lynn K. , Van Voorhis Wesley C. , Lukehart Sheila A.
Published: September 2003

Variation in the expression of the different Tpr proteins in the syphilis spirochete,Treponema pallidumsubsp.pallidum, may have important implications in its ability to evade host immune detection and cause persistent infection. In the present study we examined the pattern of antibody responsiveness to different Tpr members during infection with three isolates ofT. pallidum. There was variability in the specificities and temporal patterns of reactivity of the antibodies elicited against the individual Tpr proteins, suggesting that isolates may express different repertoires of Tpr proteins during infection.
Differential Contribution of Toll-Like Receptors 4 and 2 to the Cytokine Response toSalmonella entericaSerovar Typhimurium andStaphylococcus aureusin Mice
Authors: Lembo Annalisa , Kalis Christoph , Kirschning Carsten J. , Mitolo Vincenzo , Jirillo Emilio , Wagner Hermann , Galanos Chris , Freudenberg Marina A.
Published: September 2003

The contribution of murine Toll-like receptors 2 and 4 (TLR2 and -4, respectively) to cytokine induction by heat-killed bacteria was analyzed in vitro and in vivo. Gram-negative bacteria induced cytokines primarily via TLR4; the contribution of TLR2 was only minor. Neither TLR4 nor, surprisingly, TLR2 was required in the MyD88-dependent response toStaphylococcus aureus.
Sequence and Expression Analysis of
virB9
of the Type IV Secretion System of
Ehrlichia canis
Strains in Ticks, Dogs, and Cultured Cells
Authors: Felek Suleyman , Huang Haibin , Rikihisa Yasuko
Published: September 2003

Ehrlichia canis virB9
was cloned and expressed. The sequences of
virB9
from six geographic locations were identical.
virB9
was transcribed by
E. canis
in dogs, ticks, and cell culture. Infected dogs had antibodies to recombinant VirB9, indicating that VirB9 was produced by
E. canis
in dogs and was antigenic.
Host Adaptation of Pigeon Isolates of
Salmonella enterica
subsp.
enterica
Serovar Typhimurium Variant Copenhagen Phage Type 99 Is Associated with Enhanced Macrophage Cytotoxicity
Authors: Pasmans Frank , Van Immerseel Filip , Heyndrickx Marc , Martel An , Godard Claudine , Wildemauwe Christa , Ducatelle Richard , Haesebrouck Freddy
Published: September 2003

Phage type 99 of
Salmonella enterica
subsp.
enterica
serovar Typhimurium variant Copenhagen strains isolated from pigeons were examined for the presence of genotypic and phenotypic characteristics. The pulsed-field gel electrophoresis patterns obtained with
Xba
I and
Bln
I from 38 pigeon strains were compared with those obtained from 89 porcine, poultry, and human strains of variant Copenhagen. Identical patterns with
Xba
I and four closely related patterns with
Bln
I were obtained with the pigeon strains, whereas 16
Xba
I patterns were found with the other strains. The
Xba
I patterns of the pigeon strains showed a low genetic similarity to the patterns of the porcine, poultry, and human strains and invariably showed a low-molecular-weight band that was absent in the majority of the other strains. The virulence genes
shdA
,
spvR
,
pefA
,
sopE
, and
spvB
were uniformly present in six pigeon isolates representing the genetic diversity found with
Bln
I. These six pigeon-derived strains were highly cytotoxic for pigeon macrophages compared to three porcine strains. After experimental infection of pigeons with a pigeon strain, clinical symptoms, fecal shedding, and colonization of internal organs were more pronounced than those after infection with a porcine strain. These data suggest that the phage type 99 strains used in this study are highly adapted to pigeons and should be classified as a host-restricted lineage of the serovar Typhimurium.
Serum Amyloid P Component Binding to Shiga Toxin 2 Requires Both A Subunit and B Pentamer
Authors: Marcato Paola , Vander Helm Kathleen , Mulvey George L. , Armstrong Glen D.
Published: September 2003

Solid-phase binding, competitive binding, and cytotoxicity neutralization assays indicate that the B pentamer and A subunit both contribute to human serum amyloid P (HuSAP) component binding to Stx2. A polyvalent globotriaosyl-ceramide receptor analog, Daisy, did not competitively inhibit HuSAP binding, implying that the two ligands bind to different Stx2 domains.
Streptococcus pyogenes
Infection in Mouse Skin Leads to a Time-Dependent Up-Regulation of Protein H Expression
Authors: Smith Tara C. , Sledjeski Darren D. , Boyle Michael D. P.
Published: September 2003

Streptococcus pyogenes
protein H (
sph
) is an immunoglobulin-binding protein present in the Mga regulon of certain M1 serotype isolates. Although
sph
is present in many strains, it is frequently not expressed. In this paper we show that protein H was highly expressed after bacteria were injected into the skin of mice and were recovered from the blood, kidney, or spleen at various times postinfection. The percentage of protein H-positive colonies increased with time, reaching 100% in the spleen and kidney within 24 to 72 h postinfection. The up-regulation of
sph
expression was also observed in a
mga
mutant.
Analysis of Expression Profile of Mammalian Cell Entry (
mce
) Operons of
Mycobacterium tuberculosis
Authors: Kumar Ashwani , Bose Mridula , Brahmachari Vani
Published: September 2003

The sequencing of the complete genome of
M. tuberculosis
H37Rv has resulted in the recognition of four
mce
operons in its genome by in silico analysis. In an attempt to understand the significance of the redundancy of
mce
operons, we analyzed the expression profile of
mce
operons after different periods of growth in culture as well as during in vivo infection. Our results strongly suggest that
mce1
is expressed as a polycistronic message. In culture from day 8 to day 12, expression of only
mce1
was observed, but as the cultures progress towards stationary phase the expression profile of
mce
operons was altered; the transcripts of the
mce1
operon were barely detected while those of the
mce4
operon were prominent. In an analysis of the expression of
mce
operons in tubercle material collected from infected animal tissues, we detected the expression of
mce1
, -
3
and -
4
. Our results imply that
mce
operons other than
mce1
are also expressed during infection and that it is necessary to examine their role in pathogenesis.
Identification and Characterization of a New Staphylococcal Enterotoxin-Related Putative Toxin Encoded by Two Kinds of Plasmids
Authors: Omoe Katsuhiko , Hu Dong-Liang , Takahashi-Omoe Hiromi , Nakane Akio , Shinagawa Kunihiro
Published: September 2003

We identified and characterized a novel staphylococcal enterotoxin-like putative toxin, which is named SER. Nucleotide sequencing analysis of the
ser
gene revealed that
ser
was most closely related to the
seg
gene. The
ser
gene product, SER, was successfully expressed as a recombinant protein in an
Escherichia coli
expression system, and recombinant SER (rSER) showed significant T-cell stimulation activity. The SER production in
ser
-harboring
Staphylococcus aureus
strains was confirmed by Western blot analysis using anti-rSER antibody. Moreover,
ser
was seen to be encoded by at least two types of plasmids. In particular, one kind of plasmid encoding the
ser
gene has been known as a
sed
- and
sej
-carrying pIB485-related plasmid.
Streptococcus pneumoniae
Damages the Ciliated Ependyma of the Brain during Meningitis
Authors: Hirst Robert A. , Gosai Bejal , Rutman Andrew , Andrew Peter W. , O'Callaghan Christopher
Published: September 2003

Streptococcus pneumoniae
meningitis remains a disease with a poor outcome for the patient. A region of the brain that has been neglected in the study of meningitis is the ependyma, which has been identified as a location of adult pluripotent cells. In this study we have used a rat model of meningitis to examine whether the ependymal layer is affected by
S. pneumoniae
. The effects included localized loss of cilia, a decrease of the overall ependymal ciliary beat frequency, and damage to the ependymal ultrastructure during meningitis. In conclusion, loss of ependymal cells and ciliary function exposes the underlying neuronal milieu to host and bacterial cytotoxins and this is likely to contribute to the neuropathology commonly observed in pneumococcal meningitis.
Evaluation of the Roles of Four
Candida albicans
Genes in Virulence by Using Gene Disruption Strains That Express
URA3
from the Native Locus
Authors: Cheng Shaoji , Nguyen M. Hong , Zhang Zongde , Jia Hongyan , Handfield Martin , Clancy Cornelius J.
Published: September 2003

Reintroducing
URA3
to its native locus in
Candida albicans not5
,
not3
,
bur2
, and
kel1
disruption mutants enabled us to directly compare strains with control strain CAI-12. We showed that
URA3
position affected orotidine 5′-monophosphate decarboxylase activity, hyphal morphogenesis, adherence, and mortality in murine disseminated candidiasis. After
URA3
was reintroduced to its native locus, only
NOT5
could be conclusively ascribed a role in virulence.
Identification of an Inducible Bacteriophage in a Virulent Strain of
Streptococcus suis
Serotype 2
Authors: Harel J. , Martinez G. , Nassar A. , Dezfulian H. , Labrie S. J. , Brousseau R. , Moineau S. , Gottschalk M.
Published: September 2003

Streptococcus suis
infection is considered to be a major problem in the swine industry worldwide. Most virulent Canadian isolates of
S. suis
serotype 2 do not produce the known virulence markers for this pathogen. PCR-based subtraction hybridization was adapted to isolate unique DNA sequences which were specific to virulent strains of
S. suis
isolated in Canada. Analysis of some subtracted DNA clones revealed significant homology with bacteriophages of gram-positive bacteria. An inducible phage (named Ss1) was observed in
S. suis
following the incubation of the virulent strain 89-999 with mitomycin C. Phage Ss1 has a long noncontractile tail and a small isometric nucleocapsid and is a member of the
Siphoviridae
family. Ss1 phage DNA appears to be present in most Canadian
S. suis
strains tested in this study, which were isolated from diseased pigs or had proven virulence in mouse or pig models. To our knowledge, this is the first report of the isolation of a phage in
S. suis
.
On Reasoning About Rings
Authors: Emerson E. Allen , Namjoshi Kedar S.
Published: September 2003

Distributed protocols are often composed of similar processes connected in a unidirectional ring network. Processes communicate by passing a token in a fixed direction; the process that holds the token is allowed to perform certain actions. Usually, correctness properties are expected to hold irrespective of the size of the ring. We show that the question of checking many useful correctness properties for rings of all sizes can be reduced to checking them on ring of sizes up to a small cutoff size. We apply our results to the verification of a mutual exclusion protocol and Milner's scheduler protocol.
A Generic Approach to the Static Analysis of Concurrent Programs with Procedures
Authors: Bouajjani Ahmed , Esparza Javier , Touili Tayssir
Published: September 2003

We present a generic aproach to the static analysis of concurrent programs with procedures. We model programs as communicating pushdown systems. It is known that typical dataflow problems for this model are undecidable, because the emptiness problem for the intersection of context-free languages, which is undecidable, can be reduced to them. In this paper we propose an algebraic framework for defining abstractions (upper approximations) of context-free languages. We consider two classes of abstractions: finite-chain abstractions, which are abstractions whose domains do not contain any infinite chains, and commutative abstractions corresponding to classes of languages that contain a word if and only if they contain all its permutations. We show how to compute such approximations by combining automata theoretic techniques with algorithms for solving systems of polynomial inequations in Kleene algebras.
Abstraction and Counterexample-Guided Refinement in Model Checking of Hybrid Systems
Authors: Clarke Edmund , Fehnker Ansgar , Han Zhi , Krogh Bruce , Ouaknine Joël , Stursberg Olaf , Theobald Michael
Published: September 2003

Hybrid dynamic systems include both continuous and discrete state variables. Properties of hybrid systems, which have an infinite state space, can often be verified using ordinary model checking together with a finite-state abstraction. Model checking can be inconclusive, however, in which case the abstraction must be refined. This paper presents a new procedure to perform this refinement operation for abstractions of hybrid systems. Following an approach originally developed for finite-state systems [11, 25], the refinement procedure constructs a new abstraction that eliminates a counterexample generated by the model checker. For hybrid systems, analysis of the counterexample requires the computation of sets of reachable states in the continuous state space. We show how such reachability computations with varying degrees of complexity can be used to refine hybrid system abstractions efficiently. Examples illustrate our counterexample-guided refinement procedure. Experimental results for a prototype implementation indicate significant advantages over existing methods.
Efficient Symbolic Representations for Arithmetic Constraints in Verification
Authors: Bartzis Constantinos , Bultan Tevfik
Published: September 2003

In this paper we discuss efficient symbolic representations for infinite-state systems specified using linear arithmetic constraints. We give algorithms for constructing finite automata which represent integer sets that satisfy linear constraints. These automata can represent either signed or unsigned integers and have a lower number of states compared to other similar approaches. We present efficient storage techniques for the transition function of the automata and extend the construction algorithms to formulas on both boolean and integer variables. We also derive conditions which guarantee that the pre-condition computations used in symbolic verification algorithms do not cause an exponential increase in the automata size. We experimentally compare different symbolic representations by using them to verify non-trivial concurrent systems. Experimental results show that the symbolic representations based on our construction algorithms outperform the polyhedral representation used in Omega Library, and the automata representation used in LASH.
A Logical Characterisation of Event Clock Automata
Authors: D'souza Deepak
Published: September 2003

We show that the class of Event Clock Automata [2] admit a logical characterisation via an unrestricted monadic second order logic interpreted over timed words. The result is interesting in that it provides an unrestricted yet decidable logical characterisation of a non-trivial class of timed languages. A timed temporal logic considered earlier in the literature [11] is shown to be expressively complete with respect to the monadic logic.
Characterizing Liveness Monotonicity for Weighted Petri Nets in Terms of Siphon-Based Properties
Authors: Jiao Li , Cheung To-Yat
Published: September 2003

A Petri net (N, M0) is monotonically live (m-live) if it remains live when the values of its initial marking M0 are increased. N is structurally m-live if there exists an initial marking M0 such that (N, M0) is m-live. Three new siphon-based characterizations for these properties are obtained: (1) For a weighted net N, the ST-property (i.e., every siphon contains a trap) is a necessary but not sufficient condition for N to be structurally m-live. (2) For a weighted net N, a necessary but not sufficient condition for (N, M0) to be m-live is that every siphon of N contains an M0-controlled trap (i.e., for every reachable marking M, the trap contains a place whose token value is not smaller than the least weight of its outgoing arcs). (3) A homogeneous asymmetric choice net (N, M0) is m-live if and only if every minimal siphon of N contains an M0-controlled trap. Characterization (3) is a generalization of Commoner's Theorem from ordinary liveness for ordinary free choice nets to m-liveness for homogeneous asymmetric choice nets.
A Completely Verified Realistic Bootstrap Compiler
Authors: Dold Axel , Henke Friedrich von , Goerigk Wolfgang
Published: September 2003

This paper reports on a large verification effort in constructing an initial fully trusted bootstrap compiler executable for a realistic system programming language and real target processor. The construction and verification process comprises three tasks: the verification of the compiling specification (a relation between abstract source and target programs) with respect to the language semantics and a realistic correctness criterion. This proof has been completely mechanized using the PVS verification system and is one of the largest case-studies in formal verification we are aware of. Second, the implementation of the specification in the high-level source language following a transformational approach, and finally, the implementation and verification of a binary executable written in the compiler's target language. For the latter task, a realistic technique has been developed, which is based on rigorous a-posteriori syntactic code inspection and which guarantees, for the first time, trusted execution of generated machine programs. The context of this work is the joint German research effort Verifix aiming at developing methods for the construction of correct compilers for realistic source languages and real target processors.
Distributed ω-Automata
Authors: Krithivasan Kamala , Sharda K. , Varma Sandeep V.
Published: September 2003

In this paper, we introduce the notion of distributed ω-automata. Distributed ω-automata are a group of automata working in unison to accept an ω-language. We build the theory of distributed ω-automata for finite state automata and pushdown automata in different modes of cooperation like the t-mode, *-mode, = k-mode, ≤ k-mode and ≥ k-mode along with different acceptance criteria i.e. Büchi-, Muller-, Rabin- and Streett- acceptance criteria. We then analyze the acceptance power of such automata in all the above modes of cooperation and acceptance criteria. We present proofs that distributed ω-finite state automata do not have any additional power over ω-finite state automata in any of the modes of cooperation or acceptance criteria, while distributed ω-pushdown automata can accept languages not in CFLω. We give proofs for the equivalence of all modes of cooperation and acceptance criteria in the case of distributed ω-pushdown automata. We show that the power of distributed ω-pushdown automata is equal to that of ω-Turing Machines. We also study the deterministic version of distributed ω-pushdown automata. Deterministic ω-pushdown automata accept only languages contained in CFLω but distributed deterministic ω-pushdown automata can accept languages not in CFLω and have the same power as their nondeterministic counterparts. We also define distributed completely deterministic ω-pushdown automata and analyze their power.
The Equivalence Problem of Finite Substitutions on ab*c, with Applications
Authors: Karhumäki J. , Lisovik L. P.
Published: September 2003

We show that it is undecidable whether or not two finite substitutions are equivalent on the fixed regular language ab*c. This gives an unexpected answer to a question proposed in 1985 by Culik II and Karhumäki. At the same time it can be seen as the final result in a series of undecidability results for finite transducers initiated in 1968 by Griffiths. An application to systems of equations over finite languages is given.
The Permutation Group Theory and Electrons Interaction
Authors: Tovstyuk K. D. , Tovstyuk C. C. , Danylevych O. O.
Published: September 2003

The new mathematical formalism for the Green's functions of interacting electrons in crystals is constructed. It is based on the theory of Green's functions and permutation groups. We constructed a new object of permutation groups, which we call double permutation (DP). DP allows one to take into consideration the symmetry of the ground state as well as energy and momentum conservation in every virtual interaction. We developed the classification of double permutations and proved the theorem, which allows the selection of classes of associated double permutations (ADP). The Green's functions are constructed for series of ADP. We separate in the DP the convolving columns by replacing the initial interaction between the particles with the effective interaction. In convoluting the series for Green's functions, we use the methods developed for permutation groups schemes of Young–Yamanuti.
Structural Characterisation of Silver Containing Bismuth-Borate Glasses by X-Ray Scattering
Authors: Stefan R. , Simon V. , Indrea E.
Published: September 2003

The effect of silver addition to bismuth-borate glasses with low lime content on their structure is evidenced from X-ray scattering measurements. The radius of the first coordination spheres was determined from the correlation function g(r). The larger radius values obtained for the first coordination spheres by adding silver denotes a diminution of the atom packing in this system. Further atoms from the third and fourth coordination spheres occur in a less distorted configuration than in the precursor CaO-Bi 2 O 3- B 2 O 3 vitreous compound.
Dielectric Properties of Vanadium Substituted Lithium Zinc Titanium Ferrites
Authors: Maisnam Mamata , Phanjoubam Sumitra , Sarma H. N. K. , Thakur O. P. , Devi L. Radhapiyari , Prakash Chandra
Published: September 2003

This paper reports the influence of vanadium substitution on the properties of Li – Zn – Ti ferrite. Samples with compositional formula Li 0.5+t Zn 0.2 Ti 0.2 V t Fe 2.1-2t O 4 (t ranging from 0 to 0.25 in steps of 0.05) were prepared by the conventional sintering technique. XRD analysis confirmed all the samples to be single phase with spinel structure. The lattice constant a density, Curie temperature and Saturation magnetization were measured. The dielectric behaviour was studied as a function of frequency and temperature. The dielectric behaviour showed dispersion with the frequency in the range 100 Hz to 1 MHz. The dielectric constant increases with the increase of temperature for all the samples. The possible mechanisms involved are discussed.
EPR and Magnetic Susceptibility Studies of Iron Ions in 3B2O3·CaCl2 Glass Matrix
Authors: Ardelean I. , Păşcuţă P.
Published: September 2003

Glass matrix 3B 2 O 3· CaCl 2 doped with iron ions up to 50 mol% were obtained and investigated by means of EPR and magnetic susceptibility. Information concerning the structural units involving iron ions, valence states and the type of the interactions between these ions were discussed.
Validity of Dimensional Complexity Measures of EEG Signals
Authors: Pradhan N. , Sadasivan P. K.
Published: September 2003

The measure of dimensional complexity has the potential for feature extraction, modeling and prediction of EEG signals. However, the nonlinear dynamics of neuronal processes is under criticism that EEG signals may have a simpler stochastic description and chaotic dynamical measures of EEG may be spurious or unnecessary. Surrogate-data testing has been propounded to detect nonlinearity and chaos in experimental time series and to differentiate it from linear stochastic processes or colored noises. The surrogate data tests of brain signals (EEG) have produced equivocal results. Therefore, we examine the surrogate testing procedure using numerical data of classical chaotic systems, mixed sine waves, white Gaussian and colored Gaussian noises and typical EEGs. White Gaussian noise and classical chaotic time series are easily discerned by the surrogate-data test. However, a colored Gaussian noise data of low correlation dimensions (D2) or mixed sine waves containing less number of sinusoids show behaviors similar to the low dimensional deterministic chaotic systems. There are significant differences in D2 values between the original and surrogate data sets. The colored Gaussian noise appears linear and stochastic only when there is an increased randomness in its pattern and the signal is high dimensional. Our results clearly indicate that the "surrogate testing" alone may not be a sufficient test for distinguishing colored noises from low dimensional chaos. The EEG time series produce finite correlation dimensions. The surrogate testing of 8 independent realizations of different forms of EEG activities produce significantly different D2 values than the original data sets. Apparently many natural phenomena follow deterministic chaos and as the dimensional complexity of the system increases (D2 > 5) it may approximate a stochastic process. Thus EEG appears unlikely to have originated from a linear system driven by white noise.
Bifurcation of Homoclinic Structures: I. Finite Difference Approximation and Mechanisms for Spurious Solutions
Authors: Gerling Jürgen , Jürgens Hartmut , Peitgen Heinz-Otto
Published: September 2003

In the present paper we consider the finite difference approximation for a specific nonlinear boundary value problem which generates spurious solutions. Several mechanisms for spurious solutions will be presented. The key connection is that of the homoclinic structure of an adjoint time discrete dynamical system.
Bifurcations of Symmetric Periodic Orbits Near Equilibrium in Reversible Systems
Authors: Shih Chih-Wen
Published: September 2003

Consider a family of reversible systems [Formula: see text] with the origin being an equilibrium for each μ. Suppose Dxf(0, 0) has only purely imaginary eigenvalues ±iw1,…,±iwk. We investigate the typical bifurcations of symmetric periodic solutions near the origin. A suitable complex basis is chosen so that Dxf(0, 0) and the involution are in respective simple form. Incorporated with putting f into normal form, a modified version of Lyapunov–Schmidt reduction can be applied to obtain the reduced bifurcation equations. We then focus on the cases in resonance, that is, wj = njw0, where w0 is a nonzero real number and nj is an integer for each j. Some codimension-two bifurcations are illustrated for the system in non-semisimple resonance with nj = 1, 2. A few codimension-one cases are also given for comparison with earlier works by other researchers.
Phase Breaking in a Quantum Billiard
Authors: Iitaka Toshiaki , Bird Jonathan , Stopa Michael , Ishibashi Koji , Aoyagi Yoshinobu , Sugano Takuo
Published: September 2003

We introduce a theory on phase breaking time, which predicts the temperature dependence of phase breaking time as 1/τϕ∝ kBT and geometrical effects characteristic of ballistic quantum dots. We also compare the result with the experimental data.
Chaotic Transport and Anomalous Diffusion in a Planar Flow with a Chain of Vortices
Authors: Ahn Taehoon , Kim Seunghwan
Published: September 2003

Chaotic transport in a time-periodic flow with a chain of vortices bounded by two jet regions is numerically studied using the separatrix map. The stickiness of invariant surfaces in the jet regions produces long flights of tracer particles which leads to anomalous diffusion and the algebraic decay in the probability distributions for flight lengths. For a set of parameter values of the separatrix map explored, we found crossovers in the algebraic decay, which take place at time scales for a particle to penetrate the cantori leading to the large fluctuation of the algebraic exponents and the change in the nature of diffusion at various time scales. The relation between the exponents for flights and anomalous diffusion is discussed in connection with a continuous-time random walk model, and is compared with the results from numerical experiments.
Ideal Bose Gas in Fractal Dimensions
Authors: Kim Sang-Hoon
Published: September 2003

We extended the three dimensional ideal Bose gas theory into the fractal dimensions between 2 and 3. The thermodynamic properties and critical exponents of the ideal Bose gas are studied through the functional analysis of the Bose gas function in the fractal dimensions. The condensation and phase transition of the ideal system depend on its dimensions. The phase transition is detectable only in the sufficiently high derivatives of the specific heat function. The derivatives change discontinuously at values of the fractal dimensions which we have calculated.
On Some Properties of Invariant Sets of Two-Dimensional Noninvertible Maps
Authors: Frouzakis Christos E. , Gardini Laura , Kevrekidis Ioannis G. , Millerioux Gilles , Mira Christian
Published: September 2003

We study the nature and dependence on parameters of certain invariant sets of noninvertible maps of the plane. The invariant sets we consider are unstable manifolds of saddle-type fixed and periodic points, as well as attracting invariant circles. Since for such maps a point may have more than one first-rank preimages, the geometry, transitions, and general properties of these sets are more complicated than the corresponding sets for diffeomorphisms. The critical curve(s) (locus of points having at least two coincident preimages) as well as its antecedent(s), the curve(s) where the map is singular (or "curve of merging preimages") play a fundamental role in such studies. We focus on phenomena arising from the interaction of one-dimensional invariant sets with these critical curves, and present some illustrative examples.
Absolute Stability Theory and the Synchronization Problem
Authors: Curran P. F. , Chua L. O.
Published: September 2003

Several results on synchronization by Pecora and Carroll [1991], Cuomo and Oppenheim [1993] and Wu and Chua [1994] are evaluated in the context of absolute stability theory, with significant generalizations being achieved. A robustness property of the resulting synchronization criteria is established.
Strange Nonchaotic Attractors via Torus Breakdown
Authors: Zhu Zhiwen , Liu Zhong
Published: September 2003

In this paper, we examine the quasiperiodically driven logistic map and discuss a mechanism for the development of strange nonchaotic attractors. It is shown that the attractors can be created from two-frequency torus breakdown. We find that the torus does not undergo period-doubling cascade as usual as system parameters vary, instead, the torus curve becomes extremely wrinkled, loses its smoothness and finally becomes fractal. However the Lyapunov exponent remains negative during the process. The mechanism can be used to explain the onset of strange nonchaotic behaviors in a class of systems.
n-Double Scroll Hypercubes in 1-D CNNs
Authors: Suykens J. A. K. , Chua L. O.
Published: September 2003

Unidirectional and diffusive coupling of identical n-double scroll cells in a one-dimensional cellular neural network is studied. Weak coupling between the cells leads to hyperchaos, with n-double scroll hypercube attractors observed in the common state subspace of the cells. Individually the cells remain behaving as n-double scrolls. The n-double scroll hypercubes are filled with multiple scrolls. Their birth goes through the mechanism of intermittency.
Sequences of Global Bifurcations and the Related Outcomes after Crisis of the Resonant Attractor in a Nonlinear Oscillator
Authors: Szemplińska-Stupnicka W. , Tyrkiel E.
Published: September 2003

The problem of the system behavior after annihilation of the resonant attractor in the region of the nonlinear resonance hysteresis is considered. The sequences of global bifurcations, in connection with the associated metamorphoses of basins of attraction of coexisting attractors, are examined. The study allows one to reveal the mechanism that governs the phenomenon of the post crisis ensuing transient trajectory to settle onto one or another remote attractor. The problem is studied in detail for the twin-well potential Duffing oscillator. The boundary which splits the considered region of system parameters into two subdomains, where the outcome is unique or the two outcomes are possible, is defined.
Fast Simulations of Waves in Three-Dimensional Excitable Media
Authors: Dowle Matthew , Martin Mantel Rolf , Barkley Dwight
Published: September 2003

A fast numerical scheme based on the model of Barkley [Physica 49D (1991), 61] is extended to three space dimensions (3D). The original time-stepping scheme is improved to provide greater accuracy and a 19-point approximation for the Laplacian operator in 3D is shown to have significant advantages over the commonly used 7-point formula. Simulations are coupled to a state-of-the-art surface rendering algorithm such that the combined code allows real-time interactive simulations of 3D waves on a desktop workstation. Results are presented from simulations over a range of spatio-temporal resolutions, from coarse cellular-automaton type simulations to fully resolved simulations of the underlying partial differential equations.
Stationary Structures in a Discrete Bistable Reaction–Diffusion System
Authors: Muñuzuri Alberto P. , Chua Leon O.
Published: September 2003

A detailed description of the stationary patterns observed in one-, two- and three-dimensional bistable reaction–difusion media is presented. Because of the intrinsic nature of the system, no spatial constraints are found and completely new structures arise. The mechanism stabilizing these patterns is similar to the Turing structures case for a monostable media. The most important factors determining the final stationary structures observed are also stressed out.
Neuro-Fuzzy Classifier for Astronomical Images
Authors: Revathy K. , Lekshmi S.
Published: September 2003

In this paper, we sought to determine whether fractal parameters alone are good enough in classifying astronomical images. A fuzzy membership function which follows the model of a parabola was chosen for the purpose and the success rate was found to be 73.45%. Also, we have investigated how the grade of membership functions affect the performance of a neural network classifier. For this we included the parameter, spectral flatness measure in addition to fractal dimension and the grades of both the parameters were given as input features to the neural net. It could be observed that when grades were given as inputs to the classifier, performance of the classifier has increased to 80.53%.
A Predictive Bayesian Approach to Multistate Reliability Analysis
Authors: Aven T. , Hjorteland A.
Published: September 2003

In this paper we discuss how to implement a Bayesian thinking for multistate reliability analysis. The Bayesian paradigm comprises a unified and consistent framework for analysing and expressing reliability, but in our view the standard Bayesian procedures gives too much emphasis on probability models and inference on fictional parameters. We believe that there is a need for a rethinking on how to implement the Bayesian approach, and in this paper we present and discuss such a rethinking for multistate reliability analysis. The starting point of the analysis should be observable quantities, expressing states of the world, not fictional parameters.
Bounds for the Reliability of Multistate Systems with Partially Ordered State Spaces and Stochastically Monotone Markov Transitions
Authors: Lindqvist Bo Henry
Published: September 2003

Consider a multistate system with partially ordered state space E, which is divided into a set C of working states and a set D of failure states. Let X(t) be the state of the system at time t and suppose {X(t)} is a stochastically monotone Markov chain on E. Let T be the failure time, i.e., the hitting time of the set D. We derive upper and lower bounds for the reliability of the system, defined as Pm(T > t) where m is the state of perfect system performance.
Asymptotic Approach to Reliability Analysis of Large Systems with Degrading Components
Authors: Kołowrocki Krzysztof
Published: September 2003

Basic notions of the multistate systems reliability analysis are discussed. The multistate homogeneous and non-homogeneous series, parallel, m out of n, series-parallel and parallel-series systems with degrading components are defined and their multistate reliability functions, risk functions and other characteristics are determined. The asymptotic approach to reliability analysis of large systems is defined and the notion of the multistate limit reliability function of the system is introduced. Auxiliary theorems on limit reliability functions of large multistate systems which are necessary to their approximate reliability evaluation are presented. The classes of limit reliability functions for the considered systems are fixed. Applications of the asymptotic approach to reliability evaluations of two large technical systems are presented and its accuracy is illustrated+.