bluuebunny/crossref_metadata_2025 huggingface dataset:
Chelator-Based Catheter Lock Solutions in Eradicating Organisms in Biofilm
Authors: Raad I. , Rosenblatt J. , Reitzel R. , Jiang Y. , Dvorak T. , Hachem R.
Published: October 2012

Two different chelator-based antimicrobial catheter lock solutions, methylene blue-citrate-parabens (MB-CIT) and minocycline-EDTA-25% ethanol (M-EDTA-25% ETOH), were compared in 2-h biofilm eradication experiments. Eradication of both mature and immature Gram-positive, Gram-negative, and fungal biofilms was assessed. M-EDTA-25% ETOH was able to fully eradicate all biofilms within 2 h. MB-CIT was only effective against immature biofilms but was unable to fully eradicate most of the mature biofilms tested.
Real-Time Sequencing To Decipher the Molecular Mechanism of Resistance of a Clinical Pan-Drug-Resistant Acinetobacter baumannii Isolate from Marseille, France
Authors: Rolain Jean-Marc , Diene Seydina M. , Kempf Marie , Gimenez Gregory , Robert Catherine , Raoult Didier
Published: October 2012

We compare the whole-genome sequences of two multidrug-resistant clinical
Acinetobacter baumannii
isolates recovered in the same patient before (ABIsac_ColiS susceptible to colistin and rifampin only) and after (ABIsac_ColiR resistant to colistin and rifampin) treatment with colistin and rifampin. We decipher all the molecular mechanisms of antibiotic resistance, and we found mutations in the
rpoB
gene and in the PmrAB two-component system explaining resistance to rifampin and colistin in ABIsac_ColiR, respectively.
A Mutation of the RNA Polymerase β′ Subunit (
rpoC
) Confers Cephalosporin Resistance in Bacillus subtilis
Authors: Lee Yong Heon , Nam Ki Hyun , Helmann John D.
Published: October 2012

In bacteria, mutations affecting the major catalytic subunits of RNA polymerase (encoded by
rpoB
and
rpoC
) emerge in response to a variety of selective pressures. Here we isolated a
Bacillus subtilis
strain with high-level resistance to cefuroxime (CEF). Whole-genome resequencing revealed only one missense mutation affecting an invariant residue in close proximity to the C-terminal DNA-binding domain of RpoC (G1122D). Genetic reconstruction experiments demonstrate that this substitution is sufficient to confer CEF resistance. The G1122D mutation leads to elevated expression of stress-responsive regulons, including those of extracytoplasmic function (ECF) σ factors (σ
M
, σ
W
, and σ
X
) and the general stress σ factor (σ
B
). The increased CEF resistance of the
rpoC
G1122D
strain is lost in the
sigM rpoC
G1122D
double mutant, consistent with a major role for σ
M
in CEF resistance. However, a
sigM
mutant is very sensitive to CEF, and this sensitivity is still reduced by the G1122D mutation, suggesting that other regulatory effects are also important. Indeed, the ability of the G1122D mutation to increase CEF resistance is further reduced in a triple mutant strain lacking three ECF σ factors (σ
M
, σ
W
, and σ
X
), which are known from prior studies to control overlapping sets of genes. Collectively, our findings highlight the ability of mutations in RNA polymerase to confer antibiotic resistance by affecting the activity of alternative σ factors that control cell envelope stress-responsive regulons.
Short-Term Monotherapy with IDX184, a Liver-Targeted Nucleotide Polymerase Inhibitor, in Patients with Chronic Hepatitis C Virus Infection
Authors: Lalezari Jacob , Asmuth David , Casiró Arnaldo , Vargas Hugo , Lawrence Shannon , Dubuc-Patrick Gloria , Chen Jie , McCarville Joseph , Pietropaolo Keith , Zhou Xiao-Jian , Sullivan-Bólyai John , Mayers Douglas
Published: October 2012

IDX184 is a liver-targeted prodrug of 2′-methylguanosine (2′-MeG) monophosphate. This study investigated the safety, tolerability, antiviral activity, and pharmacokinetics of IDX184 as a single agent in treatment-naïve patients with genotype-1 chronic hepatitis C virus (HCV) infection. Forty-one patients with baseline HCV RNA ≥ 5 log
10
IU/ml, alanine aminotransferase (ALT) ≤ 2.5× the upper limit of normal, and compensated liver disease were dosed. Sequential cohorts of 10 patients, randomized 8:2 (active:placebo), received 25, 50, 75, and 100 mg of IDX184 once daily for 3 days, with a 14-day follow-up. There were no safety-related treatment discontinuations or serious adverse events. The adverse events and laboratory abnormalities observed for IDX184- and placebo-treated patients were similar. At the end of the 3-day treatment period, changes from baseline in HCV RNA levels (means ± standard deviations) were −0.5 ± 0.6, −0.7 ± 0.2, −0.6 ± 0.3, and −0.7 ± 0.5 log
10
for the 25-, 50-, 75-, and 100-mg doses, respectively, while viral load remained unchanged for the pooled placebo patients (−0.05 ± 0.3 log
10
). Patients with genotype-1a and patients with genotype-1b responded similarly. Serum ALT levels decreased, especially at daily doses ≥ 75 mg. During the posttreatment period, plasma viremia and serum aminotransferase levels returned to near pretreatment levels. No resistance mutations associated with IDX184 were detected. Plasma exposure of IDX184 and its nucleoside metabolite 2′-MeG was dose related and low. Changes in plasma viral load correlated with plasma exposure of 2′-MeG. In conclusion, the results from this proof-of-concept study show that small doses of the liver-targeted prodrug IDX184 were able to deliver significant antiviral activity and support further clinical evaluation of the drug candidate.
Surveillance and Molecular Epidemiology of Klebsiella pneumoniae Isolates That Produce Carbapenemases: First Report of OXA-48-Like Enzymes in North America
Authors: Lascols Christine , Peirano Gisele , Hackel Meredith , Laupland Kevin B. , Pitout Johann D. D.
Published: October 2012

A study was designed to characterize nonrepeat isolates of carbapenemase-producing
K. pneumoniae
obtained from the SMART worldwide surveillance program during 2008 and 2009. Characterization was done by PCR and sequencing for
bla
VIM
,
bla
IMP
,
bla
NDM
,
bla
OXA
,
bla
KPC
, and plasmid-mediated quinolone resistance and virulence factors (VFs). Genetic relatedness was determined with pulsed-field gel electrophoresis (PFGE) using XbaI and multilocus sequence typing. A total of 110 isolates were included; 47 possess genes that encode
K. pneumoniae
carbapenemases (KPCs), 26 NDMs, 19 VIMs, 13 OXA-48-like, and 5 imipenems (IMPs). We identified 3 different major sequence types (STs) among 65% of the isolates (i.e., ST11 [
n
= 11], ST147 [
n
= 23], and ST258 [
n
= 38]). ST11 and ST147, producing OXA-48-like and NDMs, were found in Argentina, Turkey, Greece, Italy, and India; ST258, producing KPCs, was present in the United States, Israel, Greece, and Puerto Rico. The major STs consisted of up to 4 different pulsotypes, and each pulsotype had a specific geographical distribution. A new ST, named ST903, with
bla
IMP-26
, was identified in the Philippines, while two
bla
OXA-48
-positive isolates were detected in the United States. There were no significant differences in the distribution of the VFs between the isolates; all were positive for
fimH
,
mrkD
,
wabG
, and
ureA
. This is the first report of OXA-48-like enzymes in North America. Our study highlights the importance of surveillance programs using molecular techniques as powerful tools to identify the importance of international sequence types.
The Haemophilus influenzae Sap Transporter Mediates Bacterium-Epithelial Cell Homeostasis
Authors: Raffel Forrest K. , Szelestey Blake R. , Beatty Wandy L. , Mason Kevin M.
Published: October 2012

Nontypeable
Haemophilus influenzae
(NTHI) is a commensal inhabitant of the human nasopharynx and a causative agent of otitis media and other diseases of the upper and lower human airway. During colonization within the host, NTHI must acquire essential nutrients and evade immune attack. We previously demonstrated that the NTHI Sap transporter, an inner membrane protein complex, mediates resistance to antimicrobial peptides and is required for heme homeostasis. We hypothesized that Sap transporter functions are critical for NTHI interaction with the host epithelium and establishment of colonization. Thus, we cocultured the parent or the
sapA
mutant on polarized epithelial cells grown at an air-liquid interface, as a physiological model of NTHI colonization, to determine the contribution of the Sap transporter to bacterium-host cell interactions. Although SapA-deficient NTHI was less adherent to epithelial cells, we observed a significant increase in invasive bacteria compared to the parent strain. Upon internalization, the
sapA
mutant appeared free in the cytoplasm, whereas the parent strain was primarily found in endosomes, indicating differential subcellular trafficking. Additionally, we observed reduced inflammatory cytokine production by the epithelium in response to the
sapA
mutant strain compared to the parental strain. Furthermore, chinchilla middle ears challenged with the
sapA
mutant demonstrated a decrease in disease severity compared to ears challenged with the parental strain. Collectively, our data suggest that NTHI senses host environmental cues via Sap transporter function to mediate interaction with host epithelial cells. Epithelial cell invasion and modulation of host inflammatory cytokine responses may promote NTHI colonization and access to essential nutrients.
A systematic review of the psychological factors associated with returning to sport following injury
Authors: Ardern Clare L , Taylor Nicholas F , Feller Julian A , Webster Kate E
Published: October 2012

Background

Psychological factors have been shown to be associated with the recovery and rehabilitation period following sports injury, but less is known about the psychological response associated with returning to sport after injury. The aim of this review was to identify psychological factors associated with returning to sport following sports injury evaluated with the self-determination theory framework.

Study design

Systematic review.

Method

Electronic databases were searched from the earliest possible entry to March 2012. Quantitative studies were reviewed that included athletes who had sustained an athletic injury, reported the return to sport rate and measured at least one psychological variable. The risk of bias in each study was appraised with a quality checklist.

Results

Eleven studies that evaluated 983 athletes and 15 psychological factors were included for review. The three central elements of self-determination theory—autonomy, competence and relatedness were found to be related to returning to sport following injury. Positive psychological responses including motivation, confidence and low fear were associated with a greater likelihood of returning to the preinjury level of participation and returning to sport more quickly. Fear was a prominent emotional response at the time of returning to sport despite the fact that overall emotions became more positive as recovery and rehabilitation progressed.

Conclusions

There is preliminary evidence that positive psychological responses are associated with a higher rate of returning to sport following athletic injury, and should be taken into account by clinicians during rehabilitation.
Cost-effectiveness of total hip arthroplasty versus resurfacing arthroplasty: economic evaluation alongside a clinical trial
Authors: Edlin Richard , Tubeuf Sandy , Achten Juul , Parsons Nicholas , Costa Matthew
Published: October 2012

Objective

To report on the relative cost-effectiveness of total hip arthroplasty and resurfacing arthroplasty (replacement of articular surface of femoral head only) in patients with severe arthritis suitable for hip joint resurfacing arthroplasty.

Design

Cost-effectiveness analysis on an intention-to-treat basis of a single-centre, single-blind randomised controlled trial of 126 adult patients within 12 months of treatment. Missing data were imputed using multiple imputations with differences in baseline quality of life and gender adjusted using regression techniques.

Setting

A large teaching hospital trust in the UK.

Participants

A total of 126 adult patients with severe arthritis of the hip joint suitable for a resurfacing arthroplasty of the hip.

Results

Data were received for 126 patients, 4 of whom did not provide any resource use data. For the remainder, data were imputed for costs or quality of life in at least one time point (baseline, 3, 6 months and 1 year) for 18 patients. Patients in the resurfacing arm had higher quality of life at 12 months (0.795 vs 0.727) and received 0.032 more QALYs within the first 12 months postoperation. At an additional cost of £564, resurfacing arthroplasty offers benefits at £17 451 per QALY within the first 12 months of treatment. When covariates are considered, the health economic case is stronger in men than in women.

Conclusions

Resurfacing arthroplasty appears to offer very short-term efficiency benefits over total hip arthroplasty within a selected patient group. The short-term follow-up in this trial should be noted, particularly in light of the concerns raised regarding adverse reactions to metal debris from metal-on-metal bearing surfaces in the longer term. Longer-term follow-up of resurfacing arthroplasty patients and decision analytic modelling is also advised.

Trial registration

Current controlled TrialsISRCTN33354155. UKCRN 4093.
Experiences with global trigger tool reviews in five Danish hospitals: an implementation study
Authors: von Plessen Christian , Kodal Anne Marie , Anhøj Jacob
Published: October 2012

Objectives

To describe experiences with the implementation of global trigger tool (GTT) reviews in five Danish hospitals and to suggest ways to improve the performance of GTT review teams.

Design

Retrospective observational study.

Setting

The measurement and monitoring of harms are crucial to campaigns to improve the safety of patients. Increasingly, teams use the GTT to review patient records and measure harms in English and non-English-speaking countries. Meanwhile, it is not clear as to how the method performs in such diverse settings.

Participants

Review teams from five Danish pilot hospitals of the national Danish Safer Hospital Programme.

Primary and secondary outcome measures

We collected harm rates, background and anecdotal information and reported patient safety incidents (PSIs) from five pilot hospitals currently participating in the Danish Safer Hospital Programme. Experienced reviewers categorised harms by type. We plotted harm rates as run-charts and applied rules for the detection of patterns of non-random variation.

Results

The hospitals differed in size but had similar patient populations and activity. PSIs varied between 3 and 12 per 1000 patient-days. The average harm rate for all hospitals was 60 per 1000 patient-days ranging from 34 to 84. The percentage of harmed patients was 25 and ranged from 18 to 33. Overall, 96% of harms were temporary. Infections, pressure ulcers procedure-related and gastrointestinal problems were common. Teams reported differences in training and review procedures such as the role of the secondary reviewer.

Conclusions

We found substantial variation in harm rates. Differences in training, review procedures and documentation in patient records probably contributed to these variations. Training reviewers as teams, specifying the roles of the different reviewers, training records and a database for findings of reviews may improve the application of the GTT.
Case-mix adjusted hospital mortality is a poor proxy for preventable mortality: a modelling study
Authors: Girling Alan J , Hofer Timothy P , Wu Jianhua , Chilton Peter J , Nicholl Jonathan P , Mohammed Mohammed A , Lilford Richard J
Published: October 2012

Risk-adjustment schemes are used to monitor hospital performance, on the assumption that excess mortality not explained by case mix is largely attributable to suboptimal care. We have developed a model to estimate the proportion of the variation in standardised mortality ratios (SMRs) that can be accounted for by variation in preventable mortality. The model was populated with values from the literature to estimate a predictive value of the SMR in this context—specifically the proportion of those hospitals with SMRs among the highest 2.5% that fall among the worst 2.5% for preventable mortality. The extent to which SMRs reflect preventable mortality rates is highly sensitive to the proportion of deaths that are preventable. If 6% of hospital deaths are preventable (as suggested by the literature), the predictive value of the SMR can be no greater than 9%. This value could rise to 30%, if 15% of deaths are preventable. The model offers a ‘reality check’ for case mix adjustment schemes designed to isolate the preventable component of any outcome rate.
Dysfunction of the locus coeruleus–norepinephrine system and related circuitry in Parkinson's disease-related dementia
Authors: Del Tredici Kelly , Braak Heiko
Published: October 2012

Although resting tremor, cogwheel rigidity, hypokinesia/bradykinesia and postural instability usually dominate the clinical picture of sporadic Parkinson's disease (PD), both clinical and epidemiological data reveal that a wide variety of additional symptoms impair patients’ quality of life considerably, parallel to the chronic progressive neurodegenerative movement disorder. Autopsy based retrospective studies have shown that α-synuclein immunoreactive Lewy pathology (LP) develops in the locus coeruleus (LC) of patients with neuropathologically confirmed sporadic PD, as well as in individuals with incidental (prodromal or premotor) Lewy body disease but not in age and gender matched controls. Using five case studies, this review discusses the possible role of LP (axonopathy, cellular dysfunction and nerve cell loss) in the LC, catecholaminergic tract and related circuitry in the development of PD-related dementia. The contribution of noradrenergic deficit to cognitive dysfunction in PD has been underappreciated. Noradrenergic therapeutic interventions might not only alleviate depressive symptoms and anxiety but also delay the onset of cognitive decline.
Plasma disposition of enrofloxacin following intravenous and intramuscular administration in donkeys
Authors: Sekkin S. , Gokbulut C. , Kum C. , Karademir U.
Published: October 2012

This study was designed to investigate the plasma disposition and systemic availability of enrofloxacin (ENR) following intramuscular and intravenous administrations. Six donkeys (Equus asinus) were used in this study. The animals were allocated into two groups (intramuscular and intravenous groups). After a 2‐week washout period, the experiment was repeated with the groups reversed according to a two‐phase crossover design. In phase I, group I received intravenously the commercially available injectable solution of ENR at the dose of 5 mg/kg and group II received intramuscularly the same ENR formulation at the same dose rate. Blood samples were collected 1 hour prior to drug administration and various times between 5 minutes and 48 hours post‐treatments. The samples were analysed by high performance liquid chromatography with fluorescence detector. The half‐life and mean residence time of ENR (12.08 hours and 17.85 hours) after intramuscular route were significantly longer compared with intravenous administration (9.54 hours and 7.46 hours, respectively) and these were associated with a flip‐flop phenomenon. A marked proportion of ENR (20–21 per cent) was metabolised to ciprofloxacin (CPR) following both administration routes and the half‐life of CPR paralleled that of the parent drug after intramuscular administration. Mean absorption time was relatively long (10.39 hours), and the bioavailability of ENR was 76.56 per cent after intramuscular route in the donkeys. The plasma concentration is lower after intramuscular administration at a dose rate of 5 mg/kg, and may need a higher dose to provide sufficient plasma concentration in donkeys compared with horses.
BIOLOGICALLY INSPIRED FACE RECOGNITION: TOWARD POSE-INVARIANCE
Authors: WI NOEL TAY NUO , LOO CHU KIONG , CHOCKALINGAM LETCHUMANAN
Published: October 2012

A small change in image will cause a dramatic change in signals. Visual system is required to be able to ignore these changes, yet specific enough to perform recognition. This work intends to provide biological-backed insights into 2D translation and scaling invariance and 3D pose-invariance without imposing strain on memory and with biological justification. The model can be divided into lower and higher visual stages. Lower visual stage models the visual pathway from retina to the striate cortex (V1), whereas the modeling of higher visual stage is mainly based on current psychophysical evidences.
THE ROLE OF THE VELOCITY DISTRIBUTION IN THE DSMC PRESSURE BOUNDARY CONDITION FOR GAS MIXTURES
Authors: AHMADZADEGAN AMIR , WEN JOHN , RENKSIZBULUT METIN
Published: October 2012

A prescribed pressure is the most common flow boundary condition used in flow simulations. In the Direct Simulation Monte Carlo (DSMC) method, boundary pressure is controlled by the number flux of the simulating molecules entering the domain. In the conventional DSMC algorithm, this number flux is calculated iteratively using sampled values of velocity and number density by means of an expression derived from the Maxwell distribution function. It is known that this procedure does not work well for low speed flows which are of interest in most micro-flow applications and the statistical scatter of the DSMC results is generally stated to be the main reason. However, the Maxwell distribution used in the pressure boundary treatment is valid for equilibrium conditions, and therefore, current implementations of the DSMC pressure boundary treatment are limited to boundaries with sufficiently small rarefaction effects. This is not the case for some practical problems in which highly rarefied flows through the boundaries lead to considerable nonequilibrium effects. In this study, an expression for the species number flux is derived using the Chapman–Enskog velocity distribution to improve the pressure boundary condition. The resulting algorithm is then used for modeling a micro-channel binary gas mixture flow with prescribed pressure boundary conditions.
BALLISTIC ELECTRON TRANSPORT IN A HYBRID FERROMAGNET/TWO-DIMENSIONAL ELECTRON GAS NANOSTRUCTURE
Authors: GUO QI , XU XIAOGUANG
Published: October 2012

We have theoretically studied the ballistic electron transport in a ferromagnet/two-dimensional electron gas structure, which could be experimentally realized by depositing a magnetic metallic stripe on the top or bottom of a modulation-doped semiconductor heterostructure. The hybrid structure based on an electrical barrier with inversely proportional function and two magnetic barriers with parallel or antiparallel configurations performs high spin polarization, which strongly depends on the incident electron energy, the incident wave vector parallel to the barrier and the height of the electric potential. In addition, our numerical results show that the magneto-conductance of this structure can be strongly modulated by adjusting the incident electron energy or the electric potential.
SPATIAL CONFIGURATION OF ATOMS WITH HIGH-ENERGY ATOMIC DISPLACEMENT CASCADE IN α-Fe
Authors: WANG WEI-LU , WU XUEBANG , LIU WEI , FANG Q. F. , LIU C. S. , HUANG QUN-YING , WU Y. C.
Published: October 2012

Molecular dynamics simulations were performed to study the primary damage formation in α- Fe through collision cascades with a cascade energy of up to 100 keV. The pair analysis technique was introduced to characterize the spatial local structure distributions of atoms. The damaged microstructural unit characteristics of the body-centered cubic (bcc) crystal structure, as well as the number of point defects, followed a similar trend. Furthermore, the damaged atoms exist mostly in the microstructural characteristics of icosahedral and short-range ordering in amorphous states during and at the end of cascades. Most local spatial structures of the damaged atoms can be divided into two groups based on their corresponding non-characteristic index-pair change trends with time. The curves of the first group coincided with the vacancy (V) that exhibited one peak, whereas the curves of the second group exhibiting two peaks corresponded to the self-interstitial atoms (SIA). The maximum distance at which defects could interact with each other in space was the fifth nearest-neighbor distance of the atoms of perfect lattices in the bcc lattice. The number of local structural units of the damaged atoms that were connected with a single point defect (either V or SIA) continued to increase with increasing cascade energy by the end of the simulation. By contrast, the number of units that were connected with both V and SIA decreased. These results may help us understand the spatial configuration of atoms in the course of collision cascades.
BETA ENCODERS: SYMBOLIC DYNAMICS AND ELECTRONIC IMPLEMENTATION
Authors: KOHDA TOHRU , HORIO YOSHIHIKO , TAKAHASHI YOICHIRO , AIHARA KAZUYUKI
Published: October 2012

A new class of analog-to-digital (A/D) and digital-to-analog (D/A) converters that uses a flaky quantizer, known as a β-encoder, has been shown to have exponential bit rate accuracy and a self-correcting property for fluctuations of the amplifier factor β and quantizer threshold ν. The probabilistic behavior of this flaky quantizer is explained by the deterministic dynamics of a multivalued Rényi–Parry map on the middle interval, as defined here. This map is eventually locally onto map of [ν - 1, ν], which is topologically conjugate to Parry's (β, α)-map with α = (β - 1)(ν - 1). This viewpoint allows us to obtain a decoded sample, which is equal to the midpoint of the subinterval, and its associated characteristic equation for recovering β, which improves the quantization error by more than 3 dB when β > 1.5. The invariant subinterval under the Rényi–Parry map shows that ν should be set to around the midpoint of its associated greedy and lazy values. Furthermore, a new A/D converter referred to as the negative β-encoder is introduced, and shown to further improve the quantization error of the β-encoder. Then, a switched-capacitor (SC) electronic circuit technique is proposed for implementing A/D converter circuits based on several types of β-encoders. Electric circuit experiments were used to verify the validity of these circuits against deviations and mismatches of the circuit parameters. Finally, we demonstrate that chaotic attractors can be observed experimentally from these β-encoder circuits.
SCALING INVARIANCE IN A TIME-DEPENDENT ELLIPTICAL BILLIARD
Authors: OLIVEIRA DIEGO F. M. , ROBNIK MARKO
Published: October 2012

We study some dynamical properties of a classical time-dependent elliptical billiard. We consider periodically moving boundary and collisions between the particle and the boundary are assumed to be elastic. Our results confirm that although the static elliptical billiard is an integrable system, after introducing time-dependent perturbation on the boundary the unlimited energy growth is observed. The behavior of the average velocity is described using scaling arguments.
TIME-EVOLVING STATISTICS OF CHAOTIC ORBITS OF CONSERVATIVE MAPS IN THE CONTEXT OF THE CENTRAL LIMIT THEOREM
Authors: RUIZ G. , BOUNTIS T. , TSALLIS C.
Published: October 2012

We study chaotic orbits of conservative low-dimensional maps and present numerical results showing that the probability density functions (pdfs) of the sum of N iterates in the large N limit exhibit very interesting time-evolving statistics. In some cases where the chaotic layers are thin and the (positive) maximal Lyapunov exponent is small, long-lasting quasi-stationary states (QSS) are found, whose pdfs appear to converge to q-Gaussians associated with nonextensive statistical mechanics. More generally, however, as N increases, the pdfs describe a sequence of QSS that pass from a q-Gaussian to an exponential shape and ultimately tend to a true Gaussian, as orbits diffuse to larger chaotic domains and the phase space dynamics becomes more uniformly ergodic.
ANALYSIS OF ROUND OFF ERRORS WITH REVERSIBILITY TEST AS A DYNAMICAL INDICATOR
Authors: FARANDA DAVIDE , MESTRE MARTÍN FEDERICO , TURCHETTI GIORGIO
Published: October 2012

We compare the divergence of orbits and the reversibility error for discrete time dynamical systems. These two quantities are used to explore the behavior of the global error induced by round off in the computation of orbits. The similarity of results found for any system we have analyzed suggests the use of the reversibility error, whose computation is straightforward since it does not require the knowledge of the exact orbit, as a dynamical indicator.

The statistics of fluctuations induced by round off for an ensemble of initial conditions has been compared with the results obtained in the case of random perturbations. Significant differences are observed in the case of regular orbits due to the correlations of round off error, whereas the results obtained for the chaotic case are nearly the same.

Both the reversibility error and the orbit divergence computed for the same number of iterations on the whole phase space provide an insight on the local dynamical properties with a detail comparable with other dynamical indicators based on variational methods such as the finite time maximum Lyapunov characteristic exponent, the mean exponential growth factor of nearby orbits and the smaller alignment index. For 2D symplectic maps, the differentiation between regular and chaotic regions is well full-filled. For 4D symplectic maps, the structure of the resonance web as well as the nearby weakly chaotic regions are accurately described.
ON A CLOSENESS OF THE JULIA SETS OF NOISE-PERTURBED COMPLEX QUADRATIC MAPS
Authors: ANDREADIS IOANNIS , KARAKASIDIS THEODOROS E.
Published: October 2012

In the present work, we extend the results of the study of the structural stability of the Julia sets of noise-perturbed complex quadratic maps in the presence of dynamic and output noise both for the additive and the multiplicative cases. The critical values of the strength of the noise for which the Julia set of a family of noise-perturbed complex quadratic maps completely loses its original Julia structure were also calculated. Using graphical tools we demonstrate how one can localize the regions of the Julia sets that are affected by the presence of noise in each case. Finally, two numerical invariants for the Julia set of noise-perturbed complex quadratic maps are proposed for the study of the noise effect.
GLOBAL DYNAMICAL ANALYSIS OF HIV MODELS WITH TREATMENTS
Authors: WANG LIANCHENG
Published: October 2012

In this paper, we study HIV mathematical models with treatments. Two models with RT inhibitor and HIV protease inhibitor are studied. Local and global analysis is carried out. By identifying a critical number [Formula: see text] for both treatments, we show that if the treatment is at least [Formula: see text] effective, then the uninfected steady state P0 is the only equilibrium in the feasible region, and P0 is globally asymptotically stable. Therefore, no HIV infection persists and infected T cells and HIV virus are cleared over time. However, if the treatment is not effective enough, i.e. less than [Formula: see text], then a unique infected steady state P* emerges in the interior of the feasible region. P0 becomes unstable and the system is uniformly persistent. Therefore, HIV infection persists. In this case, the unique infected steady state can be either stable or unstable. We show that it is locally stable only for r (the proliferation rate of T cells) small or large and unstable for some intermediate values. Global stability result is established for small values of r. Numerical simulation shows that once P* becomes unstable, periodic solution appears.
SIMULATION OF HEALTHY AND EPILEPTIFORM BRAIN ACTIVITY USING CELLULAR AUTOMATA
Authors: TSOUTSOURAS VASSILIOS , SIRAKOULIS GEORGIOS Ch. , PAVLOS GEORGIOS P. , ILIOPOULOS AGGELOS C.
Published: October 2012

In this study, we first present a modeling mechanism for the loss of neurons in limbic brain regions (epileptogenic focus) that could cause epileptic seizures by spreading the pathological dynamics from the focal to healthy brain regions. Prior work has shown that Cellular Automata (CAs) are very effective in simulating physical systems and solving scientific problems by capturing essential global features of the systems resulting from the collective effect of simple system components that interact locally. Nontrivial CAs are obtained whenever the dependence on the values at each CA site is nonlinear. Consequently, in this study, we show that brain activity in a healthy and epileptic state can be simulated by CA long-range interactions. Results from analysis of CA simulation data, as well as real electroencephalographic (EEG) data clearly show the efficiency of the proposed CA algorithm for simulation of the transition to an epileptic state. The results are in agreement with ones from previous studies about the existence of high-dimensional stochastic behavior during the healthy state and low-dimensional chaotic behavior during the epileptic state. The correspondence of the CA simulation results with the ones from real EEG data analysis implies that the spatiotemporal chaotic dynamics of the epileptic brain are similar to observed nonequilibrium phase transition processes in spatially distributed complex systems.
DESYNCHRONIZATION CHAOS SHIFT KEYING METHOD BASED ON THE ERROR SECOND DERIVATIVE AND ITS SECURITY ANALYSIS
Authors: ČELIKOVSKÝ SERGEJ , LYNNYK VOLODYMYR
Published: October 2012

This paper describes the chaos shift keying method based on the second derivative desynchronization error and provides its security analysis, especially against the attacks by power and return map analysis. Desynchronization chaos shift keying method (DECSK) uses methods to detect the correct bit by detecting the wrong bit. Various modifications are possible, here the method using sharp increase of error in the second derivative of synchronizing signal is used. The proposed method requires very reasonable amount of data to encrypt and time to decrypt one bit. Basically, to encrypt one bit, only one iteration (i.e. only one real number of six valid digits) is needed. At the same time, thanks to the desynchronization detection based on the synchronization error second derivative, almost 100% of the carrying chaotic signal can be used. The security of the proposed method can be systematically investigated showing its good resistance against typical decryption attacks. More detailed analysis is devoted to its analysis via power and return map analysis. Conclusion is that the DECSK method cannot be broken by the above two methods which together with other arguments developed there serves as a good basis for the DECSK security.
Nonlinear Behaviors in Capital Structure Decisions in Australian Firms
Authors: Bahng (d'Arc) Joshua S. , Jeong Hyeong-Chul
Published: October 2012

In this paper, we investigated (i) the possible nonlinear effects in the determinants of capital structures and (ii) the nonlinear adjustment behavior of cross-sectional debt ratios in Australian firms. Our analysis utilized the quantile regression methodology and examined the existence of nonlinear relationships for Australian financial data from 1991 through 2007. In our results, we first were able to confirm the existence of nonlinear effects between debt ratio and explanatory variables such as firm size and profitability. However, this nonlinearity was not conspicuous for the independent variables of asset tangibility and non-debt tax shield. Also, the non-linear speeds of cross-sectional debt adjustment were confirmed to exist. This research introduces a new perspective on nonlinear effects into the capital structure literature and subsequently serves as a contribution to the previous literature.
Capturing Tail Risks Beyond VaR
Authors: Wong Woon Kong , Fan Guobin , Zeng Yong
Published: October 2012

Since Value-at-Risk (VaR) disregards tail losses beyond the VaR boundary, the expected shortfall (ES), which measures the average loss when a VaR is exceeded, and the tail-risk-of-VaR (TR), which sums the sizes of tail losses, are used to investigate risks at the tails of distributions for major stock markets. As VaR exceptions are rare, we employ the saddlepoint or small sample asymptotic technique to backtest ES and TR. Because the two risk measures are complementary to each other and hence provide more powerful backtests, we are able to show that (a) the correct specification of distribution tail, rather than heteroscedastic process, plays a key role to accurate risk forecasts; and (b) it is best to model the tails separately from the central part of distribution using the Generalized Pareto Distribution (GPD). To sum up, we provide empirical evidence that financial markets behave differently during crises, and extreme risks cannot be modeled effectively under normal market conditions or based on a short data history.
SHAKING TABLE TESTS AND NUMERICAL ANALYSIS FOR VERTICAL SEISMIC RESPONSE OF QUAYSIDE CONTAINER CRANES
Authors: JIN Y. L. , WU T. X. , LI Z. G.
Published: October 2012

Vertical seismic performance is an important issue for the seismic design of large-scale engineering structures. The structure, which is relatively flexible and unrestricted vertically, may resonate and its response is obviously magnified under vertical earthquake excitations. The main objective of this study is to investigate the earthquake-resistance performance of a quayside container crane under vertical seismic excitations. To this end, a geometric-scaled model of 1:50 was firstly constructed according to the similitude law. Then using this model, a hammering modal test and a series of shaking table tests were successively conducted to obtain the dynamic characteristics and vertical seismic responses. Furthermore, the experimental results were compared with the computed results of prototype obtained from numerical analysis and agreed fairly well. From dynamic response results, it is found that the large-scale structure has relatively high vertical earthquake-resistance capacity and could satisfy the seismic design requirement. The findings reported in this paper are expected to provide some valuable information for studying other similar structures in the future.
DYNAMIC INSTABILITY OF A SPINNING THICK DISK UNDER NONCONSERVATIVE TRACTION
Authors: KANG BONGSU
Published: October 2012

This paper presents the dynamic stability analysis of a spinning, thick, annular disk loaded by a circumferentially distributed frictional traction. Considering the automotive/aircraft disc brake as a representative system for this study, the brake rotor is modeled as a spinning annular disk in the context of the Mindlin's thick plate theory to ensure a more accurate estimation of the eigenvalues when the disk involves high circumferential vibration modes that are often observed in unstable disc brake rotors. The frictional traction is decomposed into in-plane and transverse components. The in-plane component is equilibrated by membrane stresses while the transverse component is a nonconservative follower-type force that is the source of the dynamic instability of the disk. The corresponding nonconservative eigenvalue problem is formulated based on the modal expansion theory for traveling waves and direct discretization technique. The brake pad or stator is modeled as a second order viscoelastic subgrade that reacts to both transverse and shearing motion of the disc brake rotor. The instability behavior of the disk is investigated by examining the resulting complex eigenvalues under various combinations of the system parameters such as frictional traction, geometry of the disk, and viscoelastic properties of the pad lining. In order to assess the effects of shear deformations and rotary inertia of the disk model under such loading conditions, results are compared with those from the classical Kirchhoff–Love's thin disk model. Based on the phase angle information of the eigenvalues, it is found that there exists a critical value of friction, slenderness ratio of the disk, and the size of pad lining at which the transverse amplitude growth rates of high circumferential vibration modes drastically increase. Unless damping is present in the disc brake rotor or pad lining, vibration modes with repeated eigenvalues are found to be always unstable either by means of divergence or flutter even for a very small nonconservative traction load.
DUAL-LEVEL DIRECT DYNAMICS STUDIES ON THE HYDROGEN ABSTRACTION REACTION OF CF3CHFCF3 (HFC-227ea) WITH Cl ATOM
Authors: ARABIEH MASOUD , ZAHEDI MANSOUR
Published: October 2012

The hydrogen abstraction reaction of CF3CHFCF3 (HFC-227ea) by Cl atom is studied theoretically over a temperature range of 50–2000 K. The reaction path information such as geometries, gradients, etc. are initially obtained at the BB1K/6-31+G (d,p) level. In order to improve the energies, high level single point energy (SPE) calculations are carried out at BB1K/MG3S on BB1K/6-31+G(d,p) geometries. The rate coefficients are obtained by dual-level direct dynamics approach with the interpolated SPE method at BB1K/MG3S//BB1K/6-31+G(d,p) level. Aforementioned rate coefficients are calculated based on canonical variational transition state theory (CVT) with small-curvature tunneling (SCT) correction. The results show that for the title reaction, variational effect is small while the tunneling effects are significant at low temperature. In order to investigate the reliability of improved BB1K potential energy surface in predicting barrier height of the reaction, different quantum models built such as QCISD(T)/6-311++G(d,p)//MP2/6-31G(d,p) , QCISD(T)/aug-cc-pv-DZ//MP2/6-31G(d,p) , and MP4SDQ/aug-cc-pv-DZ//MP2/6-31G(d,p) are applied to calculate the rate coefficients of the reaction. The results show the rate coefficients calculated based on MP2 potential energy surface are underestimated as compared to the experimental value. Finally three models are applied to fit the calculated rate coefficients over the temperature range of 50–2000 K. It is shown that the new four-parameter model provided a better temperature dependence than the other expressions. It is expected that obtained theoretical results can be useful for modeling the kinetics nature of the reaction of HFC-227ea and Cl atom over temperature range where no experimental data is accessible.
Reaction of ferricCaldariomyces fumagochloroperoxidase withmeta-chloroperoxybenzoic acid: sequential formation of compound I, compound II and regeneration of the ferric state using one reactant
Authors: Collins Daniel P. , Isaac Issa S. , Coulter Eric D. , Hager Paul W. , Ballou David P. , Dawson John H.
Published: October 2012

The mechanism of the reaction between ferric Caldariomyces fumago chloroperoxidase (CCPO) and meta-chloroperoxybenzoic acid (mCPBA) has been examined. It has previously been established that an Fe(IV) -oxo porphyrin radical species known as Compound I (Cpd I) is formed by two-electron oxidation of the native ferric enzyme by a variety of oxidants including organic peracids and hydroperoxides. Cpd I can return to the ferric state either by direct oxygen insertion into an organic substrate (e.g. a P450 oxygenase-like reaction), or by two consecutive one-electron additions, the first resulting in an intermediate Fe(IV) -oxo species known as Compound II (Cpd II). There has been much debate over the role of Cpd II and the details of its structure. In the present study, both CCPO Fe(IV) -oxo intermediates are formed, but unlike most CCPO reactions, Cpd I and Cpd II are formed using the same reactant, mCPBA. Thus, the peracid is used as an oxo donor to produce Cpd I and then as a reductant to reduce Cpd I to Cpd II, and finally, Cpd II to the ferric state. The observation of saturation kinetics with respect to mCPBA concentration for each step is consistent with the formation of CCPO-mCPBA complexes in each phase of the reaction. The original reaction mechanism for ferric CCPO with mCPBA was hypothesized to involve a scrambling mechanism with a unique Fe -OOO-C(O)R intermediate formed with no observed Cpd II intermediate. The data reported herein clearly demonstrate the formation of Cpd II in returning the oxidized enzyme back to its native ferric state.
TWO-DIMENSIONAL FINITE ELEMENT MODEL OF TEMPERATURE DISTRIBUTION IN DERMAL TISSUES OF EXTENDED SPHERICAL ORGANS OF A HUMAN BODY
Authors: MAKRARIYA AKSHARA , ADLAKHA NEERU
Published: October 2012

In the present study the thermal model of skin and subdermal tissues (SST) of human breast have been developed. The human breast is assumed to be spherical in shape with upper hemisphere projecting out from the trunk of the body and lower hemisphere is considered to be a part of the body core. The upper hemisphere represents the breast and its SST region is divided into three layers namely epidermis, dermis and subdermal tissues. The inner part of the breast represents the core/shell of the breast. The outer surface of the breast is assumed to be exposed to the environment from where the heat loss takes place by conduction, convection, radiation and evaporation. The heat transfer from core to the surface takes place by thermal conduction and blood perfusion. Also metabolic activity takes place at different rates in different SST layers of the breast. Boundary conditions have been framed on the basis of physical conditions. A finite element model has been developed for a two-dimensional steady state case.
SYNTHESIS AND FORMATION MECHANISM OF STRAIGHT CARBON MICROTUBES BY A SIMPLE IN SITU TEMPLATE APPROACH
Authors: ZHENG MINGTAO , LIU XIANGRONG , HE CHENGLONG , XIAO YONG , LEI BINGFU , DONG HANWU , ZHANG HAORAN , LIU XIAOTANG , LIU YINGLIANG
Published: October 2012

Here we report a simple in situ template approach for the synthesis of uniformly-shaped straight carbon microtubes (SCMTs) under moderate conditions, in which zinc carbonate powder and glycol were used as starting materials. The morphology and microstructure of SCMTs were characterized by SEM, TEM, HRTEM, XRD and Raman spectrum. The length and diameter of SCMTs can be controlled by simply varying the concentration of zinc carbonate in glycol. Experimental results show that ZnO nanorods generated during the process act as an in situ template for SCMT formation. Owing to their large inner spacing, SCMTs may have potential applications in supporter materials for drugs, dyes, and catalysts, microreactors, and hydrogen or energy storage materials.
Highlights from the Asia Pacific Region
Authors: APPN Editorial Office
Published: October 2012

Quantum computing promises to deliver unprecedented effciency by exploiting the laws of quantum mechanics in order to process information in ways fundamentally different from today's classical computers. As recently as a decade ago Raussendorf and Briegel proposed the one-way quantum computer which differs dramatically from the standard model of quantum computation [1]. Whereas the standard model relies on sequences of quantum logic gates that process qubits, the one-way model implements computations as a sequence of measurements on an array of highly entangled states; the so-called cluster state. A cluster state is first created as a generic resource, and the algorithms to be computed are determined by the choice and sequence of measurements, allowing us to imprint a circuit in real time as the flow of information is directed through the cluster.
The Daya Bay Experiment and the Discovery of a New Type of Neutrino Oscillation
Authors: Wang Yifang
Published: October 2012

We know nowadays that the matter world we live in is made of 12 elementary particles, including 6 quarks, 3 charged leptons and 3 neutrinos. Among them, neutrinos are least known since they do not carry the electric charge and interact with others only weakly (often referred as the nuclear weak interactions). In the Standard Model of particle physics before 1998, neutrinos are considered as massless for simplicity and lack of experimental evidence. However, they are so abundant in the universe that their masses, even if tiny, will have significant impact to the particle physics, astrophysics and cosmology.