bluuebunny/crossref_metadata_2025 huggingface dataset:
ShmR Is Essential for Utilization of Heme as a Nutritional Iron Source inSinorhizobium meliloti
Authors: Amarelle Vanesa , O'Brian Mark R. , Fabiano Elena
Published: August 2008

The bacteriumSinorhizobium melilotiis able to use heme as a nutritional iron source. Here, we show that the iron-regulatedshmRgene encodes an outer membrane protein required for growth on heme. Furthermore, anshmRmutant is resistant to the toxic heme analog gallium protoporphyrin. Thus, the receptor protein of the heme transport system has been identified inS. meliloti.
Septal Pore Cap Protein SPC18, Isolated from the Basidiomycetous Fungus
Rhizoctonia solani
, Also Resides in Pore Plugs
Authors: van Driel Kenneth G. A. , van Peer Arend F. , Grijpstra Jan , Wösten Han A. B. , Verkleij Arie J. , Müller Wally H. , Boekhout Teun
Published: August 2008

The hyphae of filamentous fungi are compartmentalized by septa that have a central pore. The fungal septa and septum-associated structures play an important role in maintaining cellular and intrahyphal homeostasis. The dolipore septa in the higher
Basidiomycota
(i.e.,
Agaricomycotina
) are associated with septal pore caps. Although the ultrastructure of the septal pore caps has been studied extensively, neither the biochemical composition nor the function of these organelles is known. Here, we report the identification of the glycoprotein SPC18 that was found in the septal pore cap-enriched fraction of the basidiomycetous fungus
Rhizoctonia solani
. Based on its N-terminal sequence, the
SPC18
gene was isolated.
SPC18
encodes a protein of 158 amino acid residues, which contains a hydrophobic signal peptide for targeting to the endoplasmic reticulum and has an N-glycosylation motif. Immunolocalization showed that SPC18 is present in the septal pore caps. Surprisingly, we also observed SPC18 being localized in some plugs. The data reported here strongly support the hypothesis that septal pore caps are derived from endoplasmic reticulum and are involved in dolipore plugging and, thus, contribute to hyphal homeostasis in basidiomycetous fungi.
The Asexual Pathogen
Aspergillus fumigatus
Expresses Functional Determinants of
Aspergillus nidulans
Sexual Development
Authors: Große Verena , Krappmann Sven
Published: August 2008

The major fungal pathogen of humans,
Aspergillus fumigatus
, lacks a defined sexual cycle, although the presence of genes encoding putative mating type idiomorphs and regulators of
Aspergillus
sexual development heightens the potential for cryptic sexuality in this deuteromycete. To test the functionality of these genetic determinants, we transferred the alpha box-encoding
mat1-1
idiomorph from an
A. fumigatus
isolate to the homothallic fertile species
Aspergillus nidulans
. Abundant formation of fruiting bodies (cleistothecia) containing viable ascospores establishes functionality of this mating type gene product in the transgenic strain. Using a similar approach, we also established that the conserved transcriptional regulator from
A. fumigatus
, the
nsdD
gene product, can act as a functional, positively acting factor for
A. nidulans
cleistothecium development; moreover, high-level expression of NsdD in the endogenous host
A. fumigatus
profoundly alters hyphal development by triggering the formation of coiled hyphae. Our findings demonstrate that the presumably asexual pathogen
A. fumigatus
encodes functional regulators of mating and sexual development, thereby potentiating the case for cryptic sexuality in this fungal pathogen.
Detection and Localization of Single LysM-Peptidoglycan Interactions
Authors: Andre Guillaume , Leenhouts Kees , Hols Pascal , Dufrêne Yves F.
Published: August 2008

The lysin motif (LysM) is a ubiquitous protein module that binds peptidoglycan and structurally related molecules. Here, we used single-molecule force spectroscopy (SMFS) to measure and localize individual LysM-peptidoglycan interactions on both model and cellular surfaces. LysM modules of the major autolysin AcmA of
Lactococcus lactis
were bound to gold-coated atomic force microscopy tips, while peptidoglycan was covalently attached onto model supports. Multiple force curves recorded between the LysM tips and peptidoglycan surfaces yielded a bimodal distribution of binding forces, presumably reflecting the occurrence of one and two LysM-peptidoglycan interactions, respectively. The specificity of the measured interaction was confirmed by performing blocking experiments with free peptidoglycan. Next, the LysM tips were used to map single LysM interactions on the surfaces of
L. lactis
cells. Strikingly, native cells showed very poor binding, suggesting that peptidoglycan was hindered by other cell wall constituents. Consistent with this notion, treatment of the cells with trichloroacetic acid, which removes peptidoglycan-associated polymers, resulted in substantial and homogeneous binding of the LysM tip. These results provide novel insight into the binding forces of bacterial LysMs and show that SMFS is a promising tool for studying the heterologous display of proteins or peptides on bacterial surfaces.
Roles and Interactions of
Burkholderia pseudomallei
BpsIR Quorum-Sensing System Determinants
Authors: Kiratisin Pattarachai , Sanmee Sittinee
Published: August 2008

The
Burkholderia pseudomallei
quorum-sensing system (QSS), designated BpsIR, is encoded by five
bpsR
genes and three
bpsI
genes. This study investigated the roles and interactions of the QSS determinants in terms of gene regulation and protein interaction. We report two novel findings, that BpsR can function as an activator and a repressor for
bpsI
expression and that BpsR may form homodimers and heterodimers.
Abundance Changes of the Response Regulator RcaC Require Specific Aspartate and Histidine Residues and Are Necessary for Normal Light Color Responsiveness
Authors: Li Lina , Kehoe David M.
Published: August 2008

RcaC is a large, complex response regulator that controls transcriptional responses to changes in ambient light color in the cyanobacterium
Fremyella diplosiphon
. The regulation of RcaC activity has been shown previously to require aspartate 51 and histidine 316, which appear to be phosphorylation sites that control the DNA binding activity of RcaC. All available data suggest that during growth in red light, RcaC is phosphorylated and has relatively high DNA binding activity, while during growth in green light RcaC is not phosphorylated and has less DNA binding activity. RcaC has also been found to be approximately sixfold more abundant in red light than in green light. Here we demonstrate that the light-controlled abundance changes of RcaC are necessary, but not sufficient, to direct normal light color responses. RcaC abundance changes are regulated at both the RNA and protein levels. The RcaC protein is significantly less stable in green light than in red light, suggesting that the abundance of this response regulator is controlled at least in part by light color-dependent proteolysis. We provide evidence that the regulation of RcaC abundance does not depend on any RcaC-controlled process but rather depends on the presence of the aspartate 51 and histidine 316 residues that have previously been shown to control the activity of this protein. We propose that the combination of RcaC abundance changes and modification of RcaC by phosphorylation may be necessary to provide the dynamic range required for transcriptional control of RcaC-regulated genes.
Aromatic Amino Acid-Dependent Expression of Indole-3-Pyruvate Decarboxylase Is Regulated by TyrR inEnterobacter cloacaeUW5
Authors: Ryu R. Julie , Patten Cheryl L.
Published: August 2008

The plant growth-promoting rhizobacteriumEnterobacter cloacaeUW5 synthesizes the plant growth hormone indole-3-acetic acid (IAA) via the indole-3-pyruvate pathway utilizing the enzyme indole-3-pyruvate decarboxylase that is encoded byipdC. In this bacterium,ipdCexpression and IAA production occur in stationary phase and are induced by an exogenous source of tryptophan, conditions that are present in the rhizosphere. The aim of this study was to identify the regulatory protein that controls the expression ofipdC. We identified a sequence in the promoter region ofipdCthat is highly similar to the recognition sequence for theEscherichia coliregulatory protein TyrR that regulates genes involved in aromatic amino acid transport and metabolism. Using atyrRinsertional mutant, we demonstrate that TyrR is required for IAA production and for induction ofipdCtranscription. TyrR directly inducesipdCexpression, as was determined by real-time quantitative reverse transcription-PCR, byipdCpromoter-driven reporter gene activity, and by electrophoretic mobility shift assays. Expression increases in response to tryptophan, phenylalanine, and tyrosine. This suggests that, in addition to its function in plant growth promotion, indolepyruvate decarboxylase may be important for aromatic amino acid uptake and/or metabolism.
Box C/D RNA-Guided 2′-O Methylations and the Intron of tRNA
Trp
Are Not Essential for the Viability of
Haloferax volcanii
Authors: Joardar Archi , Gurha Priyatansh , Skariah Geena , Gupta Ramesh
Published: August 2008

Deleting the box C/D RNA-containing intron in the
Haloferax volcanii
tRNA
Trp
gene abolishes RNA-guided 2′-O methylations of C34 and U39 residues of tRNA
Trp
. However, this deletion does not affect growth under standard conditions.
Carbon Catabolite Repression in
Bacillus subtilis
: Quantitative Analysis of Repression Exerted by Different Carbon Sources
Authors: Singh Kalpana D. , Schmalisch Matthias H. , Stülke Jörg , Görke Boris
Published: August 2008

In many bacteria glucose is the preferred carbon source and represses the utilization of secondary substrates. In
Bacillus subtilis
, this carbon catabolite repression (CCR) is achieved by the global transcription regulator CcpA, whose activity is triggered by the availability of its phosphorylated cofactors, HPr(Ser46-P) and Crh(Ser46-P). Phosphorylation of these proteins is catalyzed by the metabolite-controlled kinase HPrK/P. Recent studies have focused on glucose as a repressing substrate. Here, we show that many carbohydrates cause CCR. The substrates form a hierarchy in their ability to exert repression via the CcpA-mediated CCR pathway. Of the two cofactors, HPr is sufficient for complete CCR. In contrast, Crh cannot substitute for HPr on substrates that cause a strong repression. Determination of the phosphorylation state of HPr in vivo revealed a correlation between the strength of repression and the degree of phosphorylation of HPr at Ser46. Sugars transported by the phosphotransferase system (PTS) cause the strongest repression. However, the phosphorylation state of HPr at its His15 residue and PTS transport activity have no impact on the global CCR mechanism, which is a major difference compared to the mechanism operative in
Escherichia coli
. Our data suggest that the hierarchy in CCR exerted by the different substrates is exclusively determined by the activity of HPrK/P.
Kingella kingae
Expresses Type IV Pili That Mediate Adherence to Respiratory Epithelial and Synovial Cells
Authors: Kehl-Fie Thomas E. , Miller Sara E. , St. Geme Joseph W.
Published: August 2008

Kingella kingae
is a gram-negative bacterium that colonizes the respiratory tract and is a common cause of septic arthritis and osteomyelitis. Despite the increasing frequency of
K. kingae
disease, little is known about the mechanism by which this organism adheres to respiratory epithelium and seeds joints and bones. Previous work showed that
K. kingae
expresses long surface fibers that vary in surface density. In the current study, we found that these fibers are type IV pili and are necessary for efficient adherence to respiratory epithelial and synovial cells and that the number of pili expressed by the bacterium correlates with the level of adherence to synovial cells but not with the level of adherence to respiratory cells. In addition, we established that the major pilin subunit is encoded by a
pilA
homolog in a conserved region of the chromosome that also contains a second pilin gene and a type IV pilus accessory gene, both of which are dispensable for pilus assembly and pilus-mediated adherence. Upon examination of the
K. kingae
genome, we identified two genes in physically separate locations on the chromosome that encode homologs of the
Neisseria
PilC proteins and that have only a low level homology to each other. Examination of mutant strains revealed that both of the
K. kingae
PilC homologs are essential for a wild-type level of adherence to both respiratory epithelial and synovial cells. Taken together, these results demonstrate that type IV pili and the two PilC homologs play important roles in mediating
K. kingae
adherence.
The Extracellular Nuclease Dns and Its Role in Natural Transformation of
Vibrio cholerae
Authors: Blokesch Melanie , Schoolnik Gary K.
Published: August 2008

Free extracellular DNA is abundant in many aquatic environments. While much of this DNA will be degraded by nucleases secreted by the surrounding microbial community, some is available as transforming material that can be taken up by naturally competent bacteria. One such species is
Vibrio cholerae
, an autochthonous member of estuarine, riverine, and marine habitats and the causative agent of cholera, whose competence program is induced after colonization of chitin surfaces. In this study, we investigate how
Vibrio cholerae
's two extracellular nucleases, Xds and Dns, influence its natural transformability. We show that in the absence of Dns, transformation frequencies are significantly higher than in its presence. During growth on a chitin surface, an increase in transformation efficiency was found to correspond in time with increasing cell density and the repression of
dns
expression by the quorum-sensing regulator HapR. In contrast, at low cell density, the absence of HapR relieves
dns
repression, leading to the degradation of free DNA and to the abrogation of the transformation phenotype. Thus, as cell density increases,
Vibrio cholerae
undergoes a switch from nuclease-mediated degradation of extracellular DNA to the uptake of DNA by bacteria induced to a state of competence by chitin. Taken together, these results suggest the following model: nuclease production by low-density populations of
V. cholerae
might foster rapid growth by providing a source of nucleotides for the repletion of nucleotide pools. In contrast, the termination of nuclease production by static, high-density populations allows the uptake of intact DNA and coincides with a phase of potential genome diversification.
Characterization of
irvR
, a Novel Regulator of the
irvA
-Dependent Pathway Required for Genetic Competence and Dextran-Dependent Aggregation in
Streptococcus mutans
Authors: Niu Guoqing , Okinaga Toshinori , Zhu Lin , Banas Jeffrey , Qi Felicia , Merritt Justin
Published: August 2008

Previous studies identified
irvA
as a normally repressed but highly inducible transcription regulator capable of repressing mutacin I gene expression in
Streptococcus mutans
. In this study, we aimed to identify and characterize the regulator(s) responsible for repressing the expression of
irvA
. An uncharacterized open reading frame (SMU.1398) located immediately adjacent to
irvA
and annotated as a putative transcription repressor was identified as a likely candidate. The results of mutation studies confirmed that the expression of
irvA
was greatly increased in the SMU.1398 background. Mutation of SMU.1398 (“
irvR
”) abolished genetic competence and reduced the expression of the late competence genes/operons
comEA
,
comY
, and
dprA
without affecting the expression of the known competence regulators
comC
,
comED
, or
comX
. In addition,
irvR
was found to be a potent negative regulator of dextran-dependent aggregation (DDAG) and
gbpC
expression. Each of these
irvR
mutant phenotypes could be rescued with a double mutation of
irvA
or complemented by introducing a wild-type copy of
irvR
on a shuttle vector. These data indicate that the repression of
irvA
is critically dependent upon
irvR
and that
irvA
repression is essential for the development of genetic competence and the proper control of DDAG in
S. mutans
.
Characterization of the
Caulobacter crescentus
Holdfast Polysaccharide Biosynthesis Pathway Reveals Significant Redundancy in the Initiating Glycosyltransferase and Polymerase Steps
Authors: Toh Evelyn , Kurtz Harry D. , Brun Yves V.
Published: August 2008

Caulobacter crescentus
cells adhere to surfaces by using an extremely strong polar adhesin called the holdfast. The polysaccharide component of the holdfast is comprised in part of oligomers of
N
-acetylglucosamine. The genes involved in the export of the holdfast polysaccharide and the anchoring of the holdfast to the cell were previously discovered. In this study, we identified a cluster of polysaccharide biosynthesis genes (
hfsEFGH
) directly adjacent to the holdfast polysaccharide export genes. Sequence analysis indicated that these genes are involved in the biosynthesis of the minimum repeat unit of the holdfast polysaccharide. HfsE is predicted to be a UDP-sugar lipid-carrier transferase, the glycosyltransferase that catalyzes the first step in polysaccharide biosynthesis. HfsF is predicted to be a flippase, HfsG is a glycosyltransferase, and HfsH is similar to a polysaccharide (chitin) deacetylase. In-frame
hfsG
and
hfsH
deletion mutants resulted in severe deficiencies both in surface adhesion and in binding to the holdfast-specific lectin wheat germ agglutinin. In contrast,
hfsE
and
hfsF
mutants exhibited nearly wild-type levels of adhesion and holdfast synthesis. We identified three paralogs to
hfsE
, two of which are redundant to
hfsE
for holdfast synthesis. We also identified a redundant paralog to the
hfsC
gene, encoding the putative polysaccharide polymerase, and present evidence that the
hfsE
and
hfsC
paralogs, together with the
hfs
genes, are absolutely required for proper holdfast synthesis.
Regulation by Nucleoid-Associated Proteins at the
Escherichia coli nir
Operon Promoter
Authors: Browning Douglas F. , Cole Jeffrey A. , Busby Stephen J. W.
Published: August 2008

The
Escherichia coli
K-12
nir
operon promoter can be fully activated by binding of the regulator of fumarate and nitrate reduction (FNR) to a site centered at position −41.5 upstream of the transcript start, and this activation is modulated by upstream binding of the integration host factor (IHF) and Fis (factor for inversion stimulation) proteins. Thus, transcription initiation is repressed by the binding of IHF and Fis to sites centered at position −88 (IHF I) and position −142 (Fis I) and activated by IHF binding to a site at position −115 (IHF II). Here, we have exploited mutational analysis and biochemistry to investigate the actions of IHF and Fis at these sites. We show that the effects of IHF and Fis are position dependent and that IHF II functions independently of IHF I and Fis I. Using in vitro assays, we report that IHF and Fis repress transcription initiation by interfering with RNA polymerase binding. Differences in the upstream IHF and Fis binding sites at the
nir
promoter in related enteric bacteria fix the level of
nir
operon expression under anaerobic growth conditions.
Molecular Phylogeny of the Salmonellae: Relationships among
Salmonella
Species and Subspecies Determined from Four Housekeeping Genes and Evidence of Lateral Gene Transfer Events
Authors: McQuiston J. R. , Herrera-Leon S. , Wertheim B. C. , Doyle J. , Fields P. I. , Tauxe R. V. , Logsdon J. M.
Published: August 2008

The salmonellae are a diverse group of bacteria within the family
Enterobacteriaceae
that includes two species,
Salmonella enterica
and
Salmonella bongori
. In order to characterize the phylogenetic relationships of the species and subspecies of
Salmonella
, we analyzed four housekeeping genes,
gapA, phoP, mdh
and
recA
, comprising 3,459 bp of nucleotide sequence data for each isolate sequenced. Sixty-one isolates representing the most common serotypes of the seven subspecies of
Salmonella enterica
and six isolates of
Salmonella bongori
were included in this study. We present a robust phylogeny of the
Salmonella
species and subspecies that clearly defines the lineages comprising diphasic and monophasic subspecies. Evidence of intersubspecies lateral gene transfer of the housekeeping gene
recA
, which has not previously been reported, was obtained.
Cytological distinction between high-risk and low-risk human papillomavirus infections in SurePath liquid-based cell preparations
Authors: Wong N K S , Ng F Y , Leung G
Published: August 2008

Aims:

To investigate the correlation of various diagnostic cytological features in SurePath liquid-based cell preparations with high-risk human papillomavirus (HPV) infection.

Methods:

Case–control study. SurePath specimens from 510 cases that had been tested for HPV DNA by Hybrid Capture 2 assay were retrieved and re-examined for 10 cytological features. Distribution of these features in high- and low-risk HPV types was compared and risk statistics were estimated. Effects of cervicitis on the manifestation of HPV cytological changes were adjusted by means of logistic regression.

Results:

Cytological features of nuclear hyperchromasia, multinucleation and atypical metaplastic cells were predominantly noted in high-risk HPV infection in the category of atypical squamous cells of undetermined significance/low-grade squamous intraepithelial lesion. The odds ratios of these three features were 6–12 times higher in high-risk than low-risk HPV infection.

Conclusions:

Some diagnostic cytological features can be used as markers in Pap smear screening for assessing the types of HPV infection.
COMPUTING THE ENTROPY OF KERR–NEWMAN BLACK HOLE WITHOUT BRICK WALLS METHOD
Authors: ZHANG LI-CHUN , WU YUE-QIN , LI HUAI-FAN , REN ZHAO
Published: September 2008

By using the entanglement entropy method, the statistical entropy of the Bose and Fermi fields in a thin film is calculated and the Bekenstein–Hawking entropy of Kerr–Newman black hole is obtained. Here, the Bose and Fermi fields are entangled with the quantum states in Kerr–Newman black hole and are outside of the horizon. The divergence of brick-wall model is avoided without any cutoff by the new equation of state density obtained with the generalized uncertainty principle. The calculation implies that the high density quantum states near the event horizon are strongly correlated with the quantum states in black hole. The black hole entropy is a quantum effect. It is an intrinsic characteristic of space–time. The ultraviolet cutoff in the brick-wall model is unreasonable. The generalized uncertainty principle should be considered in the high energy quantum field near the event horizon. From the calculation, the constant λ introduced in the generalized uncertainty principle is related to polar angle θ in an axisymmetric space–time.
GENERALIZED QUANTUM FIELD THEORY BASED ON A NONLINEAR DEFORMED HEISENBERG ALGEBRA
Authors: RIBEIRO-SILVA C. I. , OLIVEIRA-NETO N. M.
Published: September 2008

We consider a quantum field theory based on a nonlinear Heisenberg algebra which describes phenomenologically a composite particle. Perturbative computation, considering the λϕ4 interaction was done and we also performed some comparison with a quantum field theory based on the q-oscillator algebra.
RECENT OBSERVATION OF SHORT-RANGE NUCLEON CORRELATIONS IN NUCLEI AND THEIR IMPLICATIONS FOR THE STRUCTURE OF NUCLEI AND NEUTRON STARS
Authors: FRANKFURT LEONID , SARGSIAN MISAK , STRIKMAN MARK
Published: September 2008

Novel processes probing the decay of nucleus after removal of a nucleon with momentum larger than Fermi momentum by hard probes finally proved unambiguously the evidence for long sought presence of short-range correlations (SRC's) in nuclei. In combination with the analysis of large Q2, A(e, e')X processes at x > 1 they allow us to conclude that (i) practically all nucleons with momenta ≥ 300 MeV /c belong to SRC's, consisting mostly of two nucleons, (ii) probability of such SRC's in medium and heavy nuclei is ~25%, (iii) a fast removal of such nucleon practically always leads to emission of correlated nucleon with approximately opposite momentum, (iv) proton removal from two-nucleon SRC's in 90% of cases is accompanied by a removal of a neutron and only in 10% by a removal of another proton. We explain that observed absolute probabilities and the isospin structure of two nucleon SRC's confirm the important role that tensor forces play in internucleon interactions. We also find that the presence of SRC's requires modifications of the Landau Fermi liquid approach to highly asymmetric nuclear matter and leads to a significantly faster cooling of cold neutron stars with neutrino cooling operational even for Np/Nn ≤ 0.1. The effect is even stronger for the hyperon stars. Theoretical challenges raised by the discovered dominance of nucleon degrees of freedom in SRC's and important role of the spontaneously broken chiral symmetry in quantum chromodynamics (QCD) in resolving them are considered. We also outline directions for future theoretical and experimental studies of the physics relevant for SRC's.
RESONANCES FOR A HYDROGENIC SYSTEM OR A HARMONIC OSCILLATOR STRONGLY COUPLED TO A FIELD
Authors: BILLIONNET CLAUDE
Published: September 2008

We calculate resonances which are formed by a particle in a potential which is either Coulombian or quadratic when the particle is strongly coupled to a massless boson, taking only two energy levels into consideration. From these calculations we derive how the moving away of the particle from its attraction center goes together with the energy lowering of hybrid states that this particle forms with the field. We study the width of these states and we show that stable states may also appear in the coupling.
MAGNETIC PROPERTIES OF Yb1-xGaxBa2Cu3O7-δ HIGH TC SUPERCONDUCTORS
Authors: POP IULIU , SBÂRCIOG CARMEN , POP OVIDIU
Published: September 2008

The thermal variation of the static magnetic susceptibility, for the Yb 1-x Ga x Ba 2 Cu 3 O 7-δ, x = 0.00; 0.01; 0.02; 0.03; 0.06 oxidic high TC superconductors was investigated. In the paramagnetic region, the reciprocal magnetic susceptibility temperature dependence is nonlinear, obeying the hyperbolic Neel law, valid for the ferromagnetic collinear magnetic structure. The effective magnetic moment value determined from the Curie constant is a giant one, suggesting the existence of Cu 3+ and Yb 6+ valence states in high TC superconducting compounds.

The structural X-ray investigation revealed a homogeneous orthorhombic crystalline structure in Yb 1-x Ga x Ba 2 Cu 3 O 7-δ superconducting compounds.
CHAOS SYNCHRONIZATION OF CHEN SYSTEM AND ITS APPLICATION TO SECURE COMMUNICATION
Authors: WANG XINGYUAN , WU XIANGJUN , HE YIJIE , ANIWAR GULZILA
Published: September 2008

This paper describes the chaos synchronization of two identical Chen systems theoretically and numerically. Based on Lyapunov stability theory, the controllers for achieving synchronization of two identical Chen systems using the PC method, active control method, and feedback method are designed. Numerical simulations show the correctness of the results. Moreover, as an application, the well-known PC method is applied to chaos-synchronization-based secure communication. Simulation results verify the proposed scheme's effectiveness in the communication application and also show its well robustness.
COMBINED EFFECTS OF SMALL SCALE ANISOTROPY AND COMPRESSIBILITY ON ANOMALOUS SCALING OF A PASSIVE SCALAR
Authors: JURČIŠINOVÁ E. , JURČIŠIN M. , REMECKY R. , SCHOLTZ M.
Published: September 2008

The model of a passive scalar field advected by the compressible Gaussian strongly anisotropic velocity field with the covariance ∝ δ(t - t′)|x - x′|2ε is studied using the field theoretic renormalization group and the operator product expansion. The inertial-range stability of the corresponding scaling regime is established. The anomalous scaling of the single-time structure functions is studied and the corresponding anomalous exponents are calculated. Their dependence on the compressibility parameter and anisotropy parameters is analyzed. It is shown that, as in the isotropic case, the presence of compressibility leads to the decrease of the critical dimensions of the important composite operators, i.e., the anomalous scaling is more pronounced in the compressible systems. All calculations are done to the first order in ε.
CONTINUUM COUPLED-MAP APPROACH TO PATTERN FORMATION IN OSCILLATING GRANULAR LAYERS: ROBUSTNESS AND LIMITATION
Authors: HARRISON MARY ANN F. , LAI YING-CHENG
Published: September 2008

Continuum coupled maps have been proposed as a generic and universal class of models to understand pattern formation in oscillating granular layers. Such models usually involve two features: Temporal period doubling in local maps and spatial coupling. The models can generate various patterns that bear striking similarities to those observed in real experiments. Here we ask two questions: (1) How robust are patterns generated by continuum coupled maps? and (2) Are there limitations, at a quantitative level, to the continuum coupled-map approach? We address the first question by investigating the effects of noise and spatial inhomogeneity on patterns generated. We also propose a measure to characterize the sharpness of the patterns. This allows us to demonstrate that patterns generated by the model are robust to random perturbations in both space and time. For the second question, we investigate the temporal scaling behavior of the disorder function, which has been proposed to characterize experimental patterns in granular layers. We find that patterns generated by continuum coupled maps do not exhibit scaling behaviors observed in experiments, suggesting that the coupled map approach, while insightful at a qualitative level, may not yield behaviors that are of importance to pattern characterization at a more quantitative level.
MULTISTABILITY AND SUBTHRESHOLD ENDEMIC STATES IN A MODEL FOR THE DYNAMICS OF NONSTERILIZING HIV VACCINES
Authors: VELASCO-HERNÁNDEZ JORGE X. , TAPIA-SANTOS BRENDA
Published: September 2008

A mathematical model for a nonsterilizing vaccine is studied. The model considers a vaccination policy represented by the vaccine application rate, waning and an index of reduction of viral load. The model also incorporates the possibility of escape mutants that avoid vaccine action. The main result is that we can show the existence of an endemic equilibrium point when R0 is less than one. The reason behind it is the existence of escape mutants that promote an increased rate of infection large enough to trigger an increase in the density of infected people even in the subthreshold case.
DIFFUSION, INTERMITTENCY, AND NOISE-SUSTAINED METASTABLE CHAOS IN THE LORENZ EQUATIONS: EFFECTS OF NOISE ON MULTISTABILITY
Authors: TUNG WEN-WEN , HU JING , GAO JIANBO , BILLOCK VINCENT A.
Published: September 2008

Multistability is an interesting phenomenon of nonlinear dynamical systems. To gain insights into the effects of noise on multistability, we consider the parameter region of the Lorenz equations that admits two stable fixed point attractors, two unstable periodic solutions, and a metastable chaotic "attractor". Depending on the values of the parameters, we observe and characterize three interesting dynamical behaviors: (i) noise induces oscillatory motions with a well-defined period, a phenomenon similar to stochastic resonance but without a weak periodic forcing; (ii) noise annihilates the two stable fixed point solutions, leaving the originally transient metastable chaos the only observable; and (iii) noise induces hopping between one of the fixed point solutions and the metastable chaos, a three-state intermittency phenomenon.
MULTISTABLE CHAOTIC DYNAMICAL SYSTEMS AND PHILOSOPHY
Authors: ABOITES VICENTE
Published: September 2008

It is proposed that any dynamical system with coexisting chaotic attractors has an emergent property. This provides a nonreductive explanation of mental states and their high sensitivity to noise and initial conditions. If metaphysical terms result from the mental states and these are emergent properties of dynamical systems with coexisting attractors, such as the brain, it is suggested that this may provide a physical explanation of metaphysical concepts.
ELECTRIC FORCE LINES OF THE DOUBLE REISSNER–NORDSTROM EXACT SOLUTION
Authors: PAOLINO ARMANDO , PIZZI MARCO
Published: September 2008

Recently Alekseev and Belinski have presented a new exact solution to the Einstein–Maxwell equation which describes two Reissner–Nordstrom (RN) sources in reciprocal equilibrium (no struts or strings); one source is a naked singularity, the other is a black hole: this is the only possible configuration for two separable objects, apart from the well-known extreme case (mi = ei).

In the present paper, after a brief summary of this solution, we study in some detail the coordinate systems used and the main features of the gravitational and electric fields. In particular, we graph the plots of the electric force lines in three qualitatively different situations: equal-sign charges, opposite charges and the case of a naked singularity near a neutral black hole.
STATEFINDER DIAGNOSTIC FOR THE YANG–MILLS DARK ENERGY MODEL
Authors: ZHAO WEN
Published: September 2008

We study the statefinder parameters in the Yang–Mills condensate dark energy models, and find that the evolving trajectories of these models are different from those of other dark energy models. We also define two eigenfunctions of the Yang–Mills condensate dark energy models. The values of these eigenfunctions are quite close to zero if the equation of state of the Yang–Mills condensate is not far from -1, which can be used to simply differentiate between the Yang–Mills condensate models and other dark energy models.
N-DIMENSIONAL GRAVITATIONAL COLLAPSE WITH DARK ENERGY
Authors: GONÇALVES R. S. , VILLAS DA ROCHA JAIME F.
Published: September 2008

We study the evolution of an N-dimensional anisotropic fluid with kinematic self-similarity of the second kind and find a class of solutions to the Einstein field equations by assuming an equation of state where the radial pressure of the fluid is proportional to its energy density (pr= ωρ) and that the fluid moves along timelike geodesics. As in the four-dimensional case, the self-similarity requires ω = -1. The energy conditions and geometrical and physical properties of the solutions are studied. We find that, depending on the self-similar parameter α, they may represent black holes or naked singularities. We also study the presence of dark energy in some models, and find that their existence gives rise to some constraints on the dimensions of the space–times.
HADRONIC INTERACTIONS FROM LATTICE QCD
Authors: BEANE SILAS R. , ORGINOS KOSTAS , SAVAGE MARTIN J.
Published: September 2008

We present an overview of recent efforts to calculate the interactions among hadrons using lattice QCD. After outlining the techniques that are used to extract scattering parameters, we detail the latest calculations of meson–meson scattering, baryon–baryon scattering and multi-meson systems obtained with domain-wall valence quarks on the staggered MILC lattices by the NPLQCD collaboration. Estimates of the computational resources required to achieve precision results in the baryon sector are presented.
PROPERTIES OF THE SUPERHEAVY NUCLEUS 294118 AND ITS α-DECAY CHAIN IN THE RELATIVISTIC MEAN FIELD THEORY
Authors: ZHOU FANG , GUO JIAN-YOU
Published: September 2008

The superheavy nucleus 294118 and its α-decay chain have been investigated systematically in the relativistic mean-field (RMF) theory with the interactions NL3, TMA, PK1 and NLZ. The properties of ground state have been described well with the binding energies per nucleon and α-decay energies, which are reproduced as compared with the experimental data. It shows that the RMF theory is effective for studying not only the stable nuclei but also the superheavy nuclei presented here. In particular, the prolate shape predicted in the ground state of these superheavy nuclei is in agreement with the experimental data as well as other theoretical calculations.
STRANGE QUARK MATTER IN THE FRAMEWORK OF ONE GLUON EXCHANGE AND DENSITY AND TEMPERATURE DEPENDENT PARTICLE MASS MODELS
Authors: MODARRES M. , GHOLIZADE H.
Published: September 2008

We calculate the thermodynamic properties of strange quark matter by using the density and temperature dependent particle mass model of Wen et al. For the interaction Hamiltonian we use the one gluon exchange interaction obtained from the Fermi liquid picture. We let the QCD coupling (αc) be constant or vary with density and temperature. A new set of mass scalings for quarks is evaluated from the present interaction, which can be used with thermodynamic formulas derived by Wen et al. Similar to β-stable matter, no stability is found in strange quark matter. Finally, it is shown that the present equation of state of strange quark matter becomes harder with respect to that obtained using the string model, specially with non-constant QCD coupling.
A VARIABLE SAMPLE SIZE S2-EWMA CONTROL CHART FOR MONITORING THE PROCESS VARIANCE
Authors: CASTAGLIOLA PHILIPPE , CELANO GIOVANNI , FICHERA SERGIO , NUNNARI VALERIA
Published: September 2008

Monitoring the stability of measures dispersion from a process quality parameter is an important aspect of Statistical Process Control which should be carefully planned by practitioners. To perform this task, this paper proposes an adaptive EWMA chart as a practical and efficient tool. The developed EWMA chart is the Variable Sample Size (VSS) version of a static S2-EWMA control chart previously developed by one of the authors to monitor the sample variance. The way to compute the design parameters of this VSS S2-EWMA control chart is discussed and an optimal design strategy based on the Average Time to Signal (ATS) after a shift in process dispersion is presented. The statistical performance of the VSS S2-EWMA has been evaluated by means of a comparison with two other EWMA charts: the static S2-EWMA and the adaptive (VSI) S2-EWMA allowing to vary the sampling intervals. The obtained results show how the possibility of varying the sample size significantly improves the statistical performance over the static S2-EWMA; furthermore, some interesting findings suggest to implement the VSS S2-EWMA with respect to the VSI S2-EWMA when some particular process operating conditions occur.
THE INSPECTION OF ACCEPTANCE SAMPLING FOR STEP-STRESS TESTS WITH AN EQUALLY-SPACED INTERVAL CENSORING SCHEME
Authors: TSAI TZONG-RU , CHEN HSIN-HAO , LU WANBO
Published: September 2008

For reducing the experimental time and considering the purpose of administrative convenience, the article establishes an acceptance sampling procedure for the Rayleigh lifetime distribution under a step-stress test with an equally-spaced interval censoring scheme. Both producer and consumer risks are considered and an algorithm is provided to develop the ordinary acceptance sampling plans. A numerical study is conducted for evaluating the performance of the proposed method. Moreover, a numerical example is used for illustration.
A RULE-BASED SOFTWARE QUALITY CLASSIFICATION MODEL
Authors: KHOSHGOFTAAR TAGHI M. , BULLARD LOFTON A. , GAO KEHAN
Published: September 2008

A rule-based classification model is presented to identify high-risk software modules. It utilizes the power of rough set theory to reduce the number of attributes, and the equal frequency binning algorithm to partition the values of the attributes. As a result, a set of conjuncted Boolean predicates are formed. The model is inherently influenced by the practical needs of the system being modeled, thus allowing the analyst to determine which rules are to be used for classifying the fault-prone and not fault-prone modules. The proposed model also enables the analyst to control the number of rules that constitute the model. Empirical validation of the model is accomplished through a case study of a large legacy telecommunications system. The ease of rule interpretation and the transparency of the functional aspects of the model are clearly demonstrated. It is concluded that the new model is effective in achieving the software quality classification.
HIERARCHICAL SEGMENTED POINT PROCESS MODELS WITH MULTIPLE CHANGE POINTS FOR MAINTAINED SYSTEMS
Authors: SYAMSUNDAR A. , NAIKAN V. N. A.
Published: September 2008

The failure processes of maintained systems operating in a changing environment may be affected by the changes and exhibit different failure behaviour before and after the changes. Such processes exhibiting abrupt changes in failure intensities at specified times require segmented models with the process domain divided into segments at the points of changes in the environment to represent them. The individual segments can be modeled by any of the usual point process models and combined to form a composite segmented model with multiple change points. This paper proposes such segmented models with multiple change points to represent the failure processes of these systems and uses a hierarchical binary segmentation method to obtain the location of the changes. Its purpose is to quantify the impacts of changes in the environment on the failure intensities. These models are applied to the field data from an industrial setting; parameter estimates obtained and are shown to more accurately describe the failure processes of maintained system in a changing environment than the single point process models usually used. The interpretation and use of these models for maintained systems is also depicted.
DIVISIBLE LOAD DISTRIBUTION IN A NETWORK OF PROCESSORS
Authors: BATAINEH SAMEER
Published: September 2008

The paper presents a closed form solution for an optimum scheduling of a divisible job on an optimum number of processor arranged in an optimum sequence in a multilevel tree networks. The solution has been derived for a single divisible job where there is no dependency among subtasks and the root processor can either perform communication and computation at the same time. The solution is carried out through three basic theorems. One of the theorems selects the optimum number of available processors that must participate in executing a divisible job. The other solves the sequencing problem in load distribution by which we are able to find the optimum sequence for load distribution in a generalized form. Having the optimum number of processors and their sequencing for load distribution, we have developed a closed form solution that determines the optimum share of each processor in the sequence such that the finish time is minimized. Any alteration of the number of processors, their sequences, or their shares that are determined by the three theorems will increase the finish time.
PERIODICALLY REGULAR CHORDAL RINGS ARE PREFERABLE TO DOUBLE-RING NETWORKS
Authors: PARHAMI BEHROOZ
Published: September 2008

The susceptibility of ring networks to disconnection as a result of one or two node/link failures has led to a number of proposals to increase the robustness of such networks. One class of proposals, discussed primarily in the networking and communication communities, but also advocated for use in parallel and distributed systems, involves the provision of a second ring to improve system throughput during normal operation and to make alternate paths available in the event of node or link failures. With regard to the advantages just listed, chordal rings are quite similar to double-ring networks, and periodically regular chordal (PRC) rings offer the added benefit of smaller node degree compared with node-symmetric chordal rings of comparable diameters. In this paper, we note that certain double-ring networks are isomorphic to suitably constructed PRC rings, while other varieties correspond to PRC rings that closely approximate their static and dynamic attributes. These results, combined with greater flexibility and other advantages for the PRC-ring family of networks, demonstrate that PRC rings are preferable to double-ring networks in virtually all application contexts. A byproduct of our observations on the relationships among double-ring networks, generalized Petersen graphs, and PRC rings is that by amalgamating known results for these network classes, many more tools and techniques become applicable to the analysis and synthesis of robust ring networks for parallel and distributed computing. As examples of new results that can be developed with this viewpoint, we present near-optimal and fault-tolerant routing algorithms for our PRC ring networks.
COST-CONSTRAINED MINIMUM-DELAY MULTICASTING
Authors: TAYU SATOSHI , AL-MUTAIRI TURKI GHAZI , UENO SHUICHI
Published: September 2008

We consider a problem of cost-constrained minimum-delay multicasting in a network, which is to find a Steiner tree spanning the source and destination nodes such that the maximum total delay along a path from the source node to a destination node is minimized, while the sum of link costs in the tree is bounded by a constant. The problem is NP-hard even if the network is series-parallel. We present a fully polynomial time approximation scheme for the problem if the network is series-parallel.
SEPARABILITY OF TRIPARTITE QUANTUM SYSTEMS
Authors: LI MING , FEI SHAO-MING , WANG ZHI-XI
Published: September 2008

We investigate the separability of arbitrary-dimensional tripartite systems. By introducing a new operator related to transformations on the subsystems, a necessary condition for the separability of tripartite systems is presented.
STUDY OF CONTINUOUS-TIME QUANTUM WALKS ON QUOTIENT GRAPHS VIA QUANTUM PROBABILITY THEORY
Authors: SALIMI S.
Published: September 2008

In the present paper, we study the continuous-time quantum walk on quotient graphs. On such graphs, there is a straightforward reduction of the problem to a subspace that can be considerably smaller than the original one. Along the lines of reductions, by using the idea of calculation of the probability amplitudes for continuous-time quantum walk in terms of the spectral distribution associated with the adjacency matrix of graphs [Jafarizadeh and Salimi (Ann. Phys.322 (2007))], we show that the continuous-time quantum walk on original graph Γ induces a continuous-time quantum walk on quotient graph ΓH. Finally, for example, we investigate the continuous-time quantum walk on some quotient Cayley graphs.
Glutamatergic inputs to the CVLM independent of the NTS promote tonic inhibition of sympathetic vasomotor tone in rats
Authors: Mandel Daniel A. , Schreihofer Ann M.
Published: August 2008

GABAergic neurons in the caudal ventrolateral medulla (CVLM) are driven by baroreceptor inputs relayed via the nucleus tractus solitarius (NTS), and they inhibit neurons in rostral ventrolateral medulla to reduce sympathetic nerve activity (SNA) and arterial pressure (AP). After arterial baroreceptor denervation or lesions of the NTS, inhibition of the CVLM continues to increase AP, suggesting additional inputs also tonically activate the CVLM. This study examined whether the NTS contributes to baroreceptor-independent drive to the CVLM and whether glutamate promotes baroreceptor- and NTS-independent activation of the CVLM to tonically reduce SNA. In addition, we evaluated whether altering central respiratory drive, a baroreceptor-independent regulator of CVLM neurons, influences glutamatergic inputs to the CVLM. Splanchnic SNA and AP were measured in chloralose-anesthetized, ventilated, paralyzed rats. The infusion of nitroprusside decreased AP below threshold for baroreceptor afferent firing (<50 mmHg) and increased SNA to 209 ± 22% ( P < 0.05), but the subsequent inhibition of the NTS by microinjection of the GABAA agonist muscimol did not further increase SNA. In contrast, after inhibition of the NTS, blockade of glutamatergic inputs to CVLM by microinjection of kynurenate increased SNA (274 ± 54%; P < 0.05; n = 7). In vagotomized rats with baroreceptors unloaded, inhibition of glutamatergic inputs to CVLM evoked a larger rise in SNA when central respiratory drive was increased (219 ± 16% vs. 271 ± 17%; n = 5; P < 0.05). These data suggest that baroreceptor inputs provide the major drive for the NTS-mediated excitation of the CVLM. Furthermore, glutamate tonically activates the CVLM to reduce SNA independent of the NTS, and this excitatory input appears to be affected by the strength of central respiratory drive.