bluuebunny/crossref_metadata_2025 huggingface dataset:
Traffic accident modeling: some statistical issues
Authors: Sawalha Z , Sayed T
Published: December 2006

Accident prediction models are invaluable tools that have many applications in road safety analysis. However, there are certain statistical issues related to accident modeling that either deserve further attention or have not been dealt with adequately in the road safety literature. This paper discusses and illustrates how to deal with two statistical issues related to modeling accidents using Poisson and negative binomial regression. The first issue is that of model building or deciding which explanatory variables to include in an accident prediction model. The study differentiates between applications for which it is advisable to avoid model over-fitting and other applications for which it is desirable to fit the model to the data as closely as possible. It then suggests procedures for developing parsimonious models, i.e., models that are not over-fitted, and best-fit models. The second issue discussed in the paper is that of outlier analysis. The study suggests a procedure for the identification and exclusion of extremely influential outliers from the development of Poisson and negative binomial regression models. The procedures suggested for model building and conducting outlier analysis are more straightforward to apply in the case of Poisson regression models because of an added complexity presented by the shape parameter of the negative binomial distribution. The paper, therefore, presents flowcharts detailing the application of the procedures when modeling is carried out using negative binomial regression. The described procedures are then applied in the development of negative binomial accident prediction models for the urban arterials of the cities of Vancouver and Richmond located in the province of British Columbia, Canada. Key words: accident prediction models, overfitting, parsimony, outlier analysis, Poisson regression, negative binomial regression.
Evaluation of the effectiveness of single-lane two-way traffic control at maintenance and reconstruction zones
Authors: Al-Kaisy Ahmed , Kerestes Eric
Published: December 2006

This paper presents a study on evaluating traffic control at single-lane closures on two-lane two-way highways. Four traffic control strategies were investigated by this study. Those strategies involved fixed-time control, fixed-queue control, "static optimum" or convoy rule, and adaptive control. Traffic control strategies were modeled using two approaches; a deterministic approach in spreadsheet application and a stochastic approach in microscopic traffic simulation. Parametric analyses were performed using several variables that are related to traffic control at this type of lane closure. Those variables involved work zone length, average speed at work zone, lost time, traffic level, directional split, and interruptions to traffic by movement of construction vehicle and (or) equipment into and out of the construction site. Study results suggest that significant savings in average delay can be accrued by using more advanced traffic control strategies. Those savings could be as high as 53% for the range of conditions investigated by this research.Key words: work zone, flaggers, adaptive control, simulation, optimization.
Forecasting breakup water levels at Fort McMurray, Alberta, using multiple linear regression
Authors: Mahabir C , Hicks F E , Robichaud C , Fayek A Robinson
Published: December 2006

Spring breakup on northern rivers can result in ice jams that present severe flood risk to adjacent communities. Such events can occur extremely rapidly, leaving little or no advanced warning to residents. Fort McMurray, Alberta, is one such community, and at present no forecasting model exists for this site. Many of the previous studies regarding ice jam flood forecasting methods, in general, cite the lack of a comprehensive database as an obstacle to statistical modelling. This paper documents the development of an extensive database containing 106 variables, and covering the period from 1972 to 2004, that was created for ice jam forecasting on the Athabasca River. Through multiple linear regression analysis, equations were developed to model the maximum water level during spring breakup. The optimal model contained a combination of hydrological and meteorological data collected from early fall until the day before river ice breakup. The number of historical years of data, rather than the scope of variables, was found to be the major limitation in verifying the results presented in this study.Key words: river ice, breakup jam, multiple linear regression.
Water quality and construction materials in rainwater catchments across Alaska
Authors: Hart Corianne , White Daniel
Published: December 2006

Many residents of Northern regions do not have access to municipal utilities. As such, rainwater catchments are commonly used as an untreated source of drinking water. The water quality in rain catchments depends on the materials used to construct the catchment, the frequency of rainfall, the amount of water collected, the quality of the rainfall, human and animal activity in the surroundings, and the duration of the water storage. The most problematic contaminants in rainwater catchments are bacteria, volatile organic compounds (VOC), and metals such as lead, copper, and zinc. The goal of this project was to help identify the frequency and magnitude of metal contaminants in Alaskan rainwater catchments. Over 50 participants from across Alaska had their tap water sampled for lead, copper, and zinc by atomic absorption during the summer of 2003. Statistical analyses showed strong correlations between catchment material and metal concentrations in drinking water samples. Key words: rainwater catchment, water quality, atomic absorption, lead, copper, zinc.
Associations between watershed characteristics, runoff, and stream water quality: hypothesis development for watershed disturbance experiments and modelling in the Forest Watershed and Riparian Disturbance (FORWARD) project
Authors: Prepas E E , Burke J M , Whitson I R , Putz G , Smith D W
Published: December 2006

The FORWARD project, based on the Boreal Plain of Alberta, was initiated to develop models to predict the influence of watershed disturbance on runoff and stream water quality. To generate hypotheses relating to watershed controls on streams in the presence and absence of disturbance, we quantified relationships between stream variables and soil distribution in nine undisturbed small (M = 5.4 km2) watersheds for two relatively dry and snowmelt-dominated seasons (May through October 2002 and 2003). We also considered data from one harvested and two burned watersheds. Among soil types, only peatland cover had an association with runoff and water quality. Runoff and ammonium exports were positively related to peatland cover in both years (r2 = 0.50 to 0.90; P < 0.05). In the first year, additional relationships to peatland cover existed for particulate phosphorus and suspended sediment exports (r2 = 0.64 and 0.65, respectively), whereas in the second year they existed for dissolved phosphorus and dissolved organic carbon exports (r2 = 0.67 and 0.78, respectively). Hypotheses generated relate to the role of peatlands as sources for water moving toward stream channels, water exchange between streams and riparian groundwater, and the influence of disturbance and precipitation patterns on runoff generation. Key words: watershed disturbance, boreal forest, peatland, stream, suspended sediments, nutrients, runoff, forest harvest, wildfire.
Artificial neural networks and time series modelling of TP concentration in boreal streams: a comparative approach
Authors: Nour Mohamed H , Smith Daniel W , El-Din Mohamed Gamal , Prepas Ellie E
Published: December 2006

Increased nutrient concentrations in fresh waters may lead to depressed dissolved oxygen concentrations, increased cyanobacterial biomass, and potentially high levels of cyanobacterial toxin production. Phosphorus loading, during snow melt and storm events, is the main source of nutrient enrichment to water bodies on the Canadian Boreal Plain. This study compared two approaches for modelling total phosphorus (TP) concentration: autoregressive moving average with exogenous input (ARMAX) and artificial neural network (ANN) models. Derived models were applied to a small forested watershed on the Canadian Boreal Plain. Results showed that ANN outperformed ARMAX based on four measures of goodness-of-fit statistics. This study confirmed that the ANN modelling approach is superior to ARMAX in modelling time-correlated gapped data, provided step-by-step guidelines for modelling time-correlated variables, and presented a feasible alternative for modelling diffuse pollutants in small forested watersheds. Key words: watershed, snow melt, diffuse pollutants, phosphorus, artificial neural networks (ANN), time series (TS), multi-slab hidden layer, ARMAX, boreal forest.
Particle penetration through rectangular-shaped cracks
Authors: Jeng C-J , Kindzierski W B , Smith D W
Published: December 2006

An outdoor-to-indoor particle penetration experiment was undertaken to validate an air infiltration flow and particle penetration model that simulates particle transport through cracks between a pair of parallel plates. Results indicated that the infiltration flow model agreed with experimental observations, and the infiltration flow field could be assumed laminar for typical outdoor-to-indoor differential pressures (1 to 15 Pa). Observations of the particle deposition pattern on crack surfaces indicated that gravitational sedimentation was the dominant deposition mechanism for 1.4 µm particles. Particle penetration coefficient (Pp) increased monotonously with increasing differential pressure and crack height (H), and decreased monotonously with increasing crack length (L). For H > 0.305 mm, and L < 30 mm cracks, Pp was greater than 0.8 for the tested conditions and particle sizes. Complete penetration was observed for H > 0.406 mm cracks under the outdoor-to-indoor differential pressures tested. The particle penetration model was able to predict experimentally derived Pp. Key words: infiltration, particle penetration coefficient, gravitational sedimentation, Brownian diffusion.
Effect of uroguanylin on potassium and bicarbonate transport in rat renal tubules
Authors: Amorim José Benedito Oliveira , Musa-Aziz Raif , Lessa Lucilia M.A. , Malnic Gerhard , Fonteles Manassés Claudino
Published: December 2006

The effect of uroguanylin (UGN) on K+and H+secretion in the renal tubules of the rat kidney was studied using in vivo stationary microperfusion. For the study of K+secretion, a tubule was punctured to inject a column of FDC-green-colored Ringer's solution with 0.5 mmol KCl/L ± 10−6mol UGN/L, and oil was used to block fluid flow. K+activity and transepithelial potential differences (PD) were measured with double microelectrodes (K+ion-selective resin vs. reference) in the distal tubules of the same nephron. During perfusion, K+activity rose exponentially, from 0.5 mmol/L to stationary concentration, allowing for the calculation of K+secretion (JK). JKincreased from 0.63 ± 0.06 nmol·cm–2·s–1in the control group to 0.85 ± 0.06 in the UGN group (p < 0.01). PD was –51.0 ± 5.3 mV in the control group and –50.3 ± 4.98 mV in the UGN group. In the presence of 10−7mol iberiotoxin/L, the UGN effect was abolished: JKwas 0.37 ± 0.038 nmol·cm–2·s–1in the absence of, and 0.38 ± 0.025 in the presence of, UGN, indicating its action on maxi-K channels. In another series of experiments, renal tubule acidification was studied, using a similar method: proximal and distal tubules were perfused with solutions containing 25 mmol NaHCO3/L. Acidification half-time was increased both in proximal and distal segments and, as a consequence, bicarbonate reabsorption decreased in the presence of UGN (in proximal tubules, from 2.40 ± 0.26 to 1.56 ± 0.21 nmol·cm–2·s–1). When the Na+/H+exchanger was inhibited by 10−4mol hexamethylene amiloride (HMA)/L, the control and UGN groups were not significantly different. In the late distal tubule, after HMA, UGN significantly reduced JHCO3–, indicating an effect of UGN on H+-ATPase. These data show that UGN stimulated JK+by acting on maxi-K channels, and decreased JHCO3–by acting on NHE3 in proximal and H+-ATPase in distal tubules.
Enhanced Ca2+sensitivity in hyperresponsive cultured bronchi is mediated by TNFα and NF-κB
Authors: Morin Caroline , Rousseau Eric
Published: December 2006

The mechanical properties and Ca2+sensitivity of an organ-culture model derived from guinea pig airways have been examined. The cultured explants develop airway hyperresponsiveness to pharmacological agonists after 3-day culture, when compared with fresh and ovalbumin-sensitized tissues. The reactivity of cultured explants is dependent on the presence of the epithelium. They are also sensitive to glucocorticosteroid pretreatments, which neutralize the TNFα antibody and ΝF-κB inhibitor. Hence, specific immunostaining of ΝF-κB subunits (p65 and p50) was increased in the nuclear extract of cultured explants. In β-escin-permeabilized preparations, step-increases in pCa revealed enhanced Ca2+sensitivity of the contractile apparatus in cultured explants, which was prevented by epithelium removal. Pretreatments of cultured explants with neutralizing TNFα antibody and ΝF-κB inhibitor consistently reduced their Ca2+sensitivity. These findings suggest that AHR developed in this organ culture model may be triggered by an inflammatory process mediated by the TNFα and NF-κB transcription factor, which results in an increased sensitivity to [Ca2+]i.
Expression of gap junctional connexins 26, 32, and 43 mRNA in ovarian preovulatory follicles and corpora lutea in sheep
Authors: Borowczyk Ewa , Johnson Mary Lynn , Bilski Jerzy J. , Borowicz Pawel P. , Redmer Dale A. , Reynolds Lawrence P. , Grazul-Bilska Anna T.
Published: December 2006

The objective of the current study was to evaluate the expression of connexins (Cx)26, Cx32, and Cx43 mRNA in granulosa and theca cells during the peri-ovulatory period (experiment 1) and in the corpus luteum (CL) during the estrous cycle (experiment 2) and during prostaglandin F2α (PGF)-induced luteal regression (experiment 3) in FSH-treated ewes. In experiment 1, Cx26, Cx32, and Cx43 mRNA was expressed in granulosa and theca cells, and expression of Cx32 and Cx43 mRNA, but not Cx26, was greater (p < 0.001) in granulosa than in theca cells throughout the peri-ovulatory period. Expression of Cx43 mRNA in granulosa and theca cells decreased (p < 0.01) 24 h after hCG treatment. In experiment 2, expression of Cx26 mRNA in the CL tended to be greater (p < 0.06) on day 10 than on days 5 or 15, but expression of Cx43 mRNA was greater (p < 0.01) on day 5 than on days 10 and 15 of the estrous cycle. In experiment 3, expression of Cx26, but not Cx32 or Cx43 mRNA decreased (p < 0.001) during PGF-induced luteal regression. In all 3 experiments, expression of Cx32 mRNA was much less than Cx26 and Cx43 mRNA. Moreover, Cx32 mRNA expression was unchanged during the peri-ovulatory period or during several stages of luteal development and PGF-induced regression of the CL. Thus, we have shown that the mRNA expression pattern of Cx26 and Cx43 changes during peri-ovulatory period and during several stages of the luteal development. This suggests that Cx26 and Cx43 play a role in ovarian tissue remodeling during the critical time around ovulation and throughout luteal tissue growth, differentiation, and regression in sheep.
Assessment of supra-additive effects of cytotoxic drugs and low dose rate irradiation in an in vitro model for hepatocellular carcinoma
Authors: Lambert Bieke , Ridder Leo De , Vos Filip De , Slegers Guido , de Gelder Virginie , de Wiele Christophe Van , Thierens Hubert
Published: December 2006

The use of 5-fluorouracil, topotecan, or gemcitabine was tested for enhancement of the effects of low dose rate (LDR) irradiation in an in vitro model for hepatocellular carcinoma. For comparison, all drugs were tested in combination with high dose rate (HDR) γ-irradiation as well. Multicellular spheroids of HepG2 cells were exposed to HDR or LDR irradiation by means of external beam cobalt-60 or rhenium-188 (188Re), respectively, dissolved in the culture medium. Secondly, exposure to irradiation was combined with the cytotoxic drug. Toxicity was evaluated by means of a quantitative spheroid outgrowth assay and histology. For 5-fluorouracil, supra-additive effects were observed in combination with HDR irradiation. With 188Re, the supra-additive toxicity was only transient. For topotecan and 188Re, no supra-additive effects were seen, whereas the addition of HDR irradiation at the end of the topotecan exposure yielded lasting supra-additive effects. Incubation with gemcitabine followed by exposure to HDR irradiation, induced a synergistic toxicity on the outgrowth. No supra-additive effects were observed when HDR irradiation was added at the start of the incubation with gemcitabine or combined with LDR irradiation. For all drugs tested, supra-additive effects were observed with HDR irradiation if the timing of the irradiation was appropriate. For 188Re, no lasting supra-additive effects were observed.
Role of 15-hydroxyeicosatetraenoic acid in phosphorylation of ERK1/2 and caldesmon in pulmonary arterial smooth muscle cells
Authors: Lu Changlian , Liu Ye , Tang Xiaobo , Ye Hong , Zhu Daling
Published: December 2006

We have reported that 15-hydroxyeicosatetraenoic acid (15-HETE) induces pulmonary artery (PA) contraction in rats exposed to hypoxia by activating extracellular signal-regulated kinase 1/2 (ERK1/2). In this study, we investigated the characteristics of 15-HETE mediating phosphorylation of ERK1/2 and caldesmon in rat pulmonary arterial smooth muscle cells (PASMCs). Our data showed that 15-HETE upregulated ERK1/2 phosphorylation in a dose-dependent manner, which could be blocked by ERK pathway inhibitors U0126 and PD98059. ERK1/2 phosphorylation was attenuated by inhibiting endogenous 15-HETE formation with lipoxygenase inhibitor, cinnamyl 3,4-dihydroxy-[alpha]-cyanocinnamate (CDC), in both normoxic and hypoxic PASMCs. ERK1/2 phosphorylation in response to 15-HETE was detected in cytosol as well as in nucleus and phosphorylatd ERK1/2 partly translocated into nucleus, which could be blocked by PD98059. In addition, caldesmon was phosphorylated in 15-HETE-stimulated cells; this could be inhibited by PD98059. These data demonstrated that 15-HETE is associated with ERK1/2 activation and caldesmon phosphorylation in PASMCs and that 15-HETE is at least partly involved in mediating activation of hypoxia-initiated ERK pathway, possibly leading to hypoxic pulmonary vasoconstriction.
Experimental infection of the endangered bonytail chub (Gila elegans) with the Asian fish tapeworm (Bothriocephalus acheilognathi): impacts on survival, growth, and condition
Authors: Hansen S.P. , Choudhury A. , Heisey D.M. , Ahumada J.A. , Hoffnagle T.L. , Cole R.A.
Published: December 2006

Bothriocephalus acheilognathi Yamaguti, 1934, a tapeworm known to be pathogenic to some fish species, has become established in the endangered humpback chub ( Gila cypha Miller, 1964) in Grand Canyon, USA, following the tapeworm’s introduction into the Colorado River system. The potential impact of this tapeworm on humpback chub was studied by exposing the closely related bonytail chub ( Gila elegans Baird and Girard, 1853) to the parasite under a range of conditions that included potential stressors of humpback chub in their natal waters, such as abrupt temperature change and a limited food base. Survival of infected fish under low food rations was considerably lower than that of control fish, and mortality of infected fish began 20 days earlier. Growth of infected fish was significantly reduced, and negative changes in health condition indices were found. No significant negative impacts were revealed from the synergistic effects between temperature shock and infection. Bothriocephalus acheilognathi does present a potential threat to humpback chub in Grand Canyon and should be considered, along with conventional concerns involving altered flow regimes and predation, when management decisions are made concerning conservation of this endangered species.
Geographic variation in the isotopic (δD, δ13C, δ15N, δ34S) composition of feathers and claws from lesser scaup and northern pintail: implications for studies of migratory connectivity
Authors: Clark Robert G. , Hobson Keith A. , Wassenaar Leonard I.
Published: December 2006

Stable hydrogen isotope (δD) measurements of bird feathers can reveal approximate North American latitudes where feathers were grown by linking feather δD values to well-defined geographic patterns in δD values in growing-season precipitation. In waterfowl, this approach may require caution because wetlands are potentially “disconnected” from predictable isotopic patterns in precipitation waters. Stable carbon (δ13C), nitrogen (δ15N), and sulphur (δ34S) isotope values of avian tissues may show geographic structure but can be complicated by land use. We analyzed claws of wintering adult northern pintails (Anas acuta L., 1758) from California and Texas, and feathers and claws of lesser scaup ( Aythya affinis (Eyton, 1838)) ducklings from northwestern North America, to determine geographic variation in δD, δ13C, δ15N, and δ34S values. Wintering pintails from Texas and California were distinguished with claw δD and δ15N values. In scaup, feather δD values differed among biomes and were positively associated with latitude; geographic variation in other isotopes was less pronounced. The δD values in feathers and claws of individual scaup ducklings were correlated. A positive relationship between scaup feather δD values and δD values in growing-season precipitation was similar to results reported for songbirds. Thus, δD values in waterfowl feathers can provide new knowledge about natal origins and moulting sites.
Mitochondrial DNA variation and matrilineal structure in blue sheep populations of Helan Mountain, China
Authors: Wang Xiao-Ming , Cao Li-Rong , Liu Zhen-Sheng , Fang Sheng-Guo
Published: December 2006

Mitochondrial DNA (mtDNA) control region (5′ hypervariable region, 554 bp) sequences from 71 samples of blue sheep ( Pseudois nayaur Hodgson, 1833) collected from six study localities throughout Helan Mountain Nature Reserve in Ningxia province of China were investigated to analyse distribution patterns of genetic variability, elucidate matrilineal structure, and investigate population history. Haplotype diversity (h) among the 71 samples was estimated to be 0.792 ± 0.037, and nucleotide diversity (Π) was relatively low (0.00392 ± 0.00046). A χ2contingency analysis of all mtDNA haplotype frequencies revealed that these haplotypes were distributed in a nonrandom fashion among study localities (χ2= 86.205, P = 0.092). Additional evidence of matrilineal structure was provided by the finding that a significant amount (9.02%; P < 0.01) of mtDNA variation was partitioned among different localities in the study area. We conclude that blue sheep of Helan Mountain Nature Reserve are structured spatially along matrilines. Pairwise computations of Φstand an AMOVA indicated that some sampling localities are differentiated relative to a random collection of genotypes and reflected differences in the spatial distribution of genetic variation. Isolation-by-distance (IBD) models (Mantel tests) revealed no obvious association between genetic differentiation and geographical distance. These results could be a basis for the development of suitable management strategies for conservation purposes. This work represents the first analysis of blue sheep mitochondrial control region DNA to be performed from a population genetics perspective.
Extinction, colonization, and distribution patterns of common eider populations nesting in a naturally fragmented landscape
Authors: Chaulk K.G. , Robertson G.J. , Montevecchi W.A.
Published: December 2006

Spatial distribution, patchy environments, and population turnover have many fundamental implications for conservation ecology. Common eider ( Somateria mollissima L., 1758) population processes were investigated in Labrador, Canada, between 1998 and 2003. We predicted that local colonies would exhibit population turnover, that extinction would be negatively related to colony and patch size, that colonization would be negatively related to island isolation, and that intraspecific incidence–abundance relationships would be positive. We found that small colonies were prone to extinction, but patch size was not a significant predictor of extinction, nor was colonization related to isolation. The overall observed annual extinction and colonization rates were 0.11 ± 0.02 and 0.41 ± 0.06, respectively, and showed variation across archipelagos. At two spatial scales we found that mean colony size was a positive predictor of island occupancy (incidence), and these relationships were maintained across years. Our findings show that common eider colonies in Labrador are dynamic and have greater turnover rates than previously expected in a species that is considered highly philopatric. Our findings support the notion that highly mobile organisms such as migratory birds can exhibit characteristics associated with metapopulation processes.
Time-concentrated sampling: a simple strategy for information gain at a novel, depleted patch
Authors: Gibson K.W. , Hall C.L. , Kramer D.L.
Published: December 2006

When an animal has found and consumed food at a new location, information about whether and when food will be present again could improve future foraging efficiency. A series of rapid returns followed by less frequent visits and finally abandonment of the patch could provide such information. By analogy with area-concentrated (area-restricted) search, we call this hypothesized pattern “time-concentrated sampling”. We tested whether eastern chipmunks ( Tamias striatus (L., 1758)) would show time-concentrated sampling in the field and whether the pattern of visits would be affected by patch value. We used peanuts to induce animals to discover a small patch of sunflower seeds. After depleting the patch, returning to find it empty, and leaving without food, 36 of 40 animals returned on sampling visits. Sampling rate was initially high and declined over 4 h. The number of peanuts and number of visits where seeds were obtained positively predicted sampling rate, but the volume of sunflower seeds presented and the distance to the burrow did not. We conclude that chipmunks exhibit flexible time-concentrated sampling.
Divergent patterns of abundance and age-class structure of headwater stream tadpoles in burned and unburned watersheds
Authors: Hossack Blake R. , Corn Paul Stephen , Fagre Daniel B.
Published: December 2006

Wildfire is a potential threat to many species with narrow environmental tolerances like the Rocky Mountain tailed frog ( Ascaphus montanus Mittleman and Myers, 1949), which inhabits a region where the frequency and intensity of wildfires are expected to increase. We compared pre- and post-fire counts of tadpoles in eight streams in northwestern Montana to determine the effects of wildfire on A. montanus. All streams were initially sampled in 2001, 2 years before four of them burned in a large wildfire, and were resampled during the 2 years following the fire. Counts of tadpoles were similar in the two groups of streams before the fire. After the fire, tadpoles were almost twice as abundant in unburned streams than in burned streams. The fire seemed to have the greatest negative effect on abundance of age-1 tadpoles, which was reflected in the greater variation in same-stream age-class structure compared with those in unburned streams. Despite the apparent effect on tadpoles, we do not expect the wildfire to be an extirpation threat to populations in the streams that we sampled. Studies spanning a chronosequence of fires, as well as in other areas, are needed to assess the effects of fires on streams with A. montanus and to determine the severity and persistence of these effects.
STUDY ON THE GLOBAL PROPERTY OF THE SMOOTH CHUA'S SYSTEM
Authors: LIAO XIAOXIN , YU PEI , XIE SHENGLI , FU YULI
Published: December 2006

In this paper, we first give a constructive proof for the existence of globally exponential attractive set of Chua's system with a smooth nonlinear function. Then, we derive a series of simple algebraic sufficient conditions under which two same type of smooth Chua's systems are globally exponentially synchronized using simple linear feedback controls. Also, as the special cases of chaos synchronization, we consider global tracking and global exponentially tracking of periodic motions, as well as global stabilization and globally exponential stabilization of equilibrium points in smooth Chua's systems. We construct a series of simple, easily applicable feedback control laws. Computer simulation results are presented to verify the theoretical predictions.
STIMULUS-INDUCED CHAOTIC SYNCHRONIZATION OF CHUA'S OSCILLATORS
Authors: KLINSHOV V. V. , KAZANTSEV V. B. , NEKORKIN V. I.
Published: December 2006

The problem of phase synchronization of Chua's chaotic oscillators is investigated. We consider Chua's circuit when it exhibits a chaotic attractor and apply a single pulse stimulus. It is shown that under certain conditions the system displays self-referential phase reset (SPR) phenomenon. This is a case when the reset phase of the chaotic oscillation is independent on the initial phase, hence on the time moment when the stimulus has been applied. In an ensemble of chaotic oscillators simultaneously stimulated, the SPR yields mutual phase coherence or synchronization between the units. We describe basic dynamical mechanisms of the effect and show how it can be used for controllable cluster formation and for the control of chaotic dynamics.
MULTIPLE BIFURCATION ANALYSIS IN A NEURAL NETWORK MODEL WITH DELAYS
Authors: YUAN YUAN , WEI JUNJIE
Published: December 2006

A synchronized neural network model with delays is considered. The bifurcations arising from the zero root of the corresponding characteristic equation have been studied by employing the center manifold theorem, normal form method and bifurcation theory. It is shown that the system may exhibit transcritical/pitchfork bifurcation, or Bogdanov–Takens bifurcation. Some numerical simulation examples are given to justify the theoretical results.
PERSISTENCE AND GLOBAL STABILITY IN A PREDATOR-PREY SYSTEM WITH DELAY
Authors: GÁMEZ MANUEL , MARTÍNEZ CLOTILDE
Published: December 2006

In this paper, several sufficient conditions are established for the persistence and extinction in a Lotka–Volterra system with time delay. Based on the use of Lyapunov functionals techniques, necessary and sufficient conditions are also given for global asymptotic stability of the positive equilibrium for autonomous systems.
ADAPTIVE SYNCHRONIZATION OF COUPLED CHAOTIC DELAYED SYSTEMS BASED ON PARAMETER IDENTIFICATION AND ITS APPLICATIONS
Authors: ZHOU JIN , CHEN TIANPING , XIANG LAN
Published: December 2006

This paper investigates synchronization dynamics of a large class of chaotic delayed systems with all the parameters unknown. By a simple combination of adaptive control and linear feedback with the updated laws, some simple yet generic criteria for determining global synchronization based on parameter identification of uncertain chaotic delayed systems are derived by using the invariance principle of functional differential equations. It is shown that the approaches developed here further extend the ideas and techniques presented in recent literature. Furthermore, the theoretical results are applied to the well-known Chua's circuit and a typical class of chaotic delayed Hopfied neural networks, and numerical simulations also demonstrate the effectiveness and feasibility of the proposed techniques.
STABILIZATION OF UNSTABLE PERIODIC SOLUTIONS BY NONLINEAR RECURSIVE DELAYED FEEDBACK CONTROL
Authors: ZHU JIANDONG , TIAN YU-PING
Published: December 2006

This paper considers stabilization of unstable periodic solutions of nonlinear systems. Based on differential geometry method, a nonlinear recursive delayed feedback controller is designed. The concept of γ dynamics is introduced and the stability of the periodic solution of the closed-loop system is proved rigorously. The proposed control method does not have the odd number limitation. Simulation results are also presented for validating the effectiveness of the proposed method.
ANALYSIS OF A MULTIPLE-OUTPUT PSEUDO-RANDOM-BIT GENERATOR BASED ON A SPATIOTEMPORAL CHAOTIC SYSTEM
Authors: LI PING , LI ZHONG , HALANG WOLFGANG A. , CHEN GUANRONG
Published: December 2006

A novel multiple-output pseudo-random-bit generator (PRBG) based on a coupled map lattice (CML) consisting of skew tent maps, which generates spatiotemporal chaos, is presented. In order to guarantee PRBG highly effective, avoiding synchronization among the sites in the CML is discussed. The cryptographic properties, such as probability distribution, auto-correlation and cross-correlation, of the PRBG with various parameters, are investigated numerically. The randomness of the PRBG is verified via FIPS 140-2. In addition, as compared with the PRBG based on the CML consisting of the logistic maps, which are often used in chaos-based PRBGs by many other researchers, the ranges of the parameters within which this multiple-output PRBG have good cryptographic properties are much bigger in terms of their cryptographic properties. It lays a foundation for designing a faster and more secure encryption.
PHENOMENOLOGY OF REACTION–DIFFUSION BINARY-STATE CELLULAR AUTOMATA
Authors: ADAMATZKY ANDREW , MARTÍNEZ GENARO JUÁREZ , MORA JUAN CARLOS SECK TUOH
Published: December 2006

We study a binary-cell-state eight-cell neighborhood two-dimensional cellular automaton model of a quasi-chemical system with a substrate and a reagent. Reactions are represented by semi-totalistic transitions rules: every cell switches from state 0 to state 1 depending on if the sum of neighbors in state 1 belongs to some specified interval, cell remains in state 1 if the sum of neighbors in state 1 belong to another specified interval. We investigate space-time dynamics of 1296 automata, establish morphology-bases classification of the rules, explore precipitating and excitatory cases and scrutinize collisions between mobile and stationary localizations (gliders, cycle life and still-life compact patterns). We explore reaction–diffusion like patterns produced as a result of collisions between localizations. Also, we propose a set of rules with complex behavior called Life 2c22.
COMPLEX DYNAMICS IN PENDULUM EQUATION WITH PARAMETRIC AND EXTERNAL EXCITATIONS II
Authors: JING ZHUJUN , YANG JIANPING
Published: December 2006

This paper (II) is a continuation of "Complex dynamics in pendulum equation with parametric and external excitations (I)." By applying second-order averaging method and Melnikov's method, we obtain the criterion of existence of chaos in an averaged system under quasi-periodic perturbation for Ω = nω + ∊ν, n = 1, 2, 4 and cannot prove the criterion of existence of chaos in averaged system under quasi-periodic perturbation for Ω = nω + ∊ν, n = 3, 5–15 by Melnikov's method, where ν is not rational to ω. However, we show the occurrence of chaos in the averaged and original systems under quasi-periodic perturbation for Ω = nω + ∊ν, n = 3, 5 by numerical simulation. The numerical simulations, include the bifurcation diagram of fixed points, bifurcation diagrams in three- and two-dimensional spaces, homoclinic bifurcation surface, maximum Lyapunov exponent, phase portraits, Poincaré map, are plotted to illustrate theoretical analysis, and to expose the complex dynamical behaviors, including period-3 orbits in different chaotic regions, interleaving occurrence of chaotic behaviors and quasi-periodic behaviors, a different kind of interior crisis, jumping behavior of quasi-periodic sets, different nice quasi-periodic attractors, nonchaotic attractors and chaotic attractors, coexistence of three quasi-periodic sets, onset of chaos which occurs more than once for a given external frequency or amplitudes, and quasi-periodic route to chaos. We do not find the period-doubling cascade. The dynamical behaviors under quasi-periodic perturbation are different from that of periodic perturbation.
STABILITY OF A GENERAL DELAY DIFFERENTIAL MODEL OF THE HYPOTHALAMO-PITUITARY-ADRENOCORTICAL SYSTEM
Authors: SAVIĆ DANKA , JELIĆ SMILJANA , BURIĆ NIKOLA
Published: December 2006

Most of the systems in an organism (human included) function in a regular daily rhythm. Hypothalamo-pituitary-adrenocortical (HPA) axis, although mostly known for its role in stress response, probably has a role in conveying rhythmic signals from the major pacemaker, suprachiazmatic nucleus (SCN), to the periphery. A general qualitative nonphenomenological mathematical model of the HPA axis is constructed and its dynamics is examined using linear stability analysis and Roushe's theorem. The results show that this system is asymptotically stable, i.e. it does not generate circadian oscillations, but only responds to the external pacemaker.
AN IDEAL DISASSORTATIVE NETWORK AND SYNCHRONIZATION
Authors: CHENGDONG DONG , ZENGRONG LIU
Published: December 2006

This paper proposes a novel complex network with disassortative property based on multicenter networks. The average path length and clustering coefficient of the network are calculated, and the impact on the network topology is investigated. A simple dynamic system established on the proposed network is used to analyze how the disassortative property of the network affects synchronization.
IMPACT OF TANDEM REPEATS ON THE SCALING OF NUCLEOTIDE SEQUENCES
Authors: NAGARAJAN RADHAKRISHNAN , UPRETI MEENAKSHI
Published: December 2006

Techniques such as detrended fluctuation analysis (DFA) and its extensions have been widely used to determine the nature of scaling in nucleotide sequences. In this brief communication we show that tandem repeats which are ubiquitous in nucleotide sequences can prevent reliable estimation of possible long-range correlations. Therefore, it is important to investigate the presence of tandem repeats prior to scaling exponent estimation.
STATIONARY OSCILLATION OF IMPULSIVE SYSTEM
Authors: LIU LI , SUN JITAO
Published: December 2006

This letter introduces two new concepts of S-stability and stationary oscillation for impulsive differential system. Based on the concept of S-stable, we present the relationship of S-stability and stationary oscillation for an impulsive system. Some criterions of stationary oscillation for the impulsive system are established. A numerical example is presented to illustrate the efficiency of the proposed result.
SLIDING MODE CONTROL OF GENERALIZED FRACTIONAL CHAOTIC SYSTEMS
Authors: EL-KHAZALI REYAD , AHMAD WAJDI , AL-ASSAF YOUSEF
Published: December 2006

A sliding mode control technique is introduced for generalized fractional chaotic systems. These systems are governed by a set of fractional differential equations of incommensurate orders. The proposed design method relies on the fact that the stability region of a fractional system contains the stability region of its underlying integer-order model. A sliding mode controller designed for an equivalent integer-order chaotic system is used to stabilize all its corresponding fractional chaotic systems. The design technique is demonstrated using two generalized fractional chaotic models; a chaotic oscillator and the Chen system. The effect of the total fractional order is investigated with respect to the controller effort and the convergence rate of the system response to the origin. Numerical simulations validate the main results of this work.
IMPACT OF GATE POLYSILICON INTERFACE ON CARRIER TRAPPING LOW FREQUENCY NOISE IN ADVANCED MOSFET'S
Authors: GHIBAUDO G. , JOMAAH J. , BALESTRA F.
Published: December 2006

In this work, we calculate, for the first time, the impact of carrier trapping at the gate polysilicon/oxide interface on the LF noise characteristics of polygate MOSFET's. After extending the channel LF noise analysis, based on carrier number and correlated mobility fluctuations approaches, to include charge variations at the polySi/oxide interface, we derive analytical expressions accounting for the impact of fluctuations of poly/oxide interfacial charge on the channel drain current and input gate voltage noise as a function of gate bias, polysilicon doping concentration and gate oxide thickness.
A RIGOROUS DERIVATION OF POWER SPECTRUM OF FRACTIONAL GAUSSIAN NOISE
Authors: LI MING , LIM S. C.
Published: December 2006

This letter gives a concise and rigorous derivation of the power spectrum density function of fractional Gaussian noise (fGn).
QUANTUM TELEPORTATION: VALUABLE MAGIC
Authors: KIM M. S.
Published: December 2006

Quantum teleportation is one of the most important manifestations of nonlocal nature. The basic theory and experiment are explained and reviewed for a qubit system and a continuous-variable system.
SUB-ENTROPIES AND PHASE PROPERTIES UNDERGOING THE EFFECTS OF ATOMIC MOTION FOR THE JAYNES–CUMMINGS MODEL WITH INITIAL MIXED STATE INPUT
Authors: OBADA A.-S. F. , HESSIAN H. A. , MOHAMED A.-B. A.
Published: December 2006

An analytical method to calculate the sub-entropies and entanglement for the mixed state as an initial field is presented. Also, we investigate the effects of the atomic motion and the field-mode structure on sub-entropies and phase properties of the coherent superposition state and a statistical mixture of coherent states as initial field states taking into account different forms of the intensity-dependent coupling. The initial state, the atomic motion and the field-mode structure play important roles in the time evolution of the entropies, entanglement and phase properties.
SHANNON INFORMATION AND ENTROPY SQUEEZING OF A SINGLE-MODE CAVITY QED OF A RAMAN INTERACTION
Authors: ABDEL-ATY MAHMOUD , AL-KHAYAT ISSA A. , HASSAN SHOUKRY S.
Published: December 2006

Entropy squeezing is examined in the framework of Shannon information entropy for a degenerate Raman process involving two degenerate Rydberg energy levels of an atom interacting with a single-mode cavity field. Quantum squeezing in entropy is exhibited via the entropic uncertainty relation.
QUANTUM STATE SHARING VIA THE GHZ STATE IN CAVITY QED WITHOUT JOINT MEASUREMENT
Authors: XUE ZHENG-YAUN , DONG PING , YI YOU-MIN , CAO ZHUO-LIANG
Published: December 2006

We investigate schemes to securely distribute and reconstruct single-qubit and two-qubit arbitrary quantum states between two parties via tripartite GHZ states in cavity QED without joint measurement. Our schemes offer a simple way of demonstrating quantum state sharing in cavity QED. We also consider the generalization of our schemes to distribute and reconstruct a quantum state among many parties.
SIMULATION OF QUANTUM ADIABATIC SEARCH IN THE PRESENCE OF NOISE
Authors: GAITAN FRANK
Published: December 2006

Results are presented of a large-scale simulation of the quantum adiabatic search (QuAdS) algorithm in the presence of noise. The algorithm is applied to the NP-Complete problem N-Bit Exact Cover 3 (EC3). The noise is assumed to Zeeman-couple to the qubits and its effects on the algorithm's performance is studied for various levels of noise power, and for four different types of noise polarization. We examine the scaling relation between the number of bits N (EC3 problem-size) and the algorithm's noise-averaged median run-time 〈T(N)〉. Clear evidence is found of the algorithm's sensitivity to noise. Two fits to the simulation results were done: (i) power-law scaling 〈T(N)〉 = aNb; and (ii) exponential scaling 〈T(N)〉 = a[ exp (bN) - 1]. Both types of scaling relations provided excellent fits, although the scaling parameters a and b varied with noise power, and with the type of noise polarization. The sensitivity of the scaling exponent b to noise polarization allows a relative assessment of which noise polarizations are most problematic for quantum adiabatic search. We demonstrate how the noise leads to decoherence in QuAdS, and estimate the amount of decoherence present in our simulations. An upper bound is also derived for the noise-averaged QuAdS success probability in the limit of weak noise that is appropriate for our simulations.
A SCHEME FOR SPATIAL WAVE FUNCTION TELEPORTATION IN THREE DIMENSIONS
Authors: AKHAVAN O. , REZAKHANI A. T. , GOLSHANI M.
Published: December 2006

We propose a theoretical scheme for teleportation of a general wave function of a quantum object. In principle, this protocol provides teleportation of discrete N-level spatial states of an object with various degrees of freedom, e.g. spin, in ordinary three-dimensional space. All necessary Bell states and their corresponding operators to measure and reconstruct the initial state are represented.
Breakthroughs in Improving Crystal Quality of GaN and Invention of the p–n Junction Blue-Light-Emitting Diode
Authors: Akasaki Isamu , Amano Hiroshi
Published: December 2006

Marked improvements in the crystalline quality of GaN enabled the production of GaN-based p–n junction blue-light-emitting and violet-laser diodes. These robust, energetically efficient devices have opened up a new frontier in optoelectronics. A new arena of wide-bandgap semiconductors has been developed due to marked improvements in the crystalline quality of nitrides. In this article, we review breakthroughs in the crystal growth and conductivity control of nitride semiconductors during the development of p–n junction blue-light-emitting devices. Recent progress mainly based on the present authors' work and future prospects of nitride semiconductors are also discussed.
Analysis of Printability of Scratch Defect on Reflective Mask in Extreme Ultraviolet Lithography
Authors: Sugawara Minoru , Nishiyama Iwao , Motai Kumi , Cullins Jerry
Published: December 2006

The aim of this study was to investigate the printability of a scratch defect on the surface of a glass substrate. Simulations revealed that smoothing deposition made a scratch more printable than non-smoothing deposition did. Smoothing deposition changes the topography of a scratch by making it shallower and wider as it propagates from the bottom to the top of a Mo/Si multilayer on a reflective mask blank. This change in topography shifts the phase, thereby reducing the energy of light reflected from the mask. In contrast, non-smoothing deposition preserves the topography of a scratch from the bottom to the top of a multilayer. As a result, non-smoothing deposition changes the phase less than smoothing deposition does, which makes a scratch less printable. An analysis of the intensity of diffracted rays clarified how much of the energy used to create a printed image was lost at the pupil due to a defect: The energy loss was approximately 10 times larger for smoothing than for non-smoothing deposition; and thus, the change in the critical dimension of a printed image on wafer was also much larger for smoothing deposition.
Effect of H2 Addition during Cu Thin-Film Sputtering
Authors: Ooka Masahiro , Yokoyama Shin
Published: December 2006

We have investigated the effect of H2 addition during Cu sputtering. It was found that the Cu surface becomes smooth with increasing amount of H2 added to Ar plasma during Cu sputtering. The arithmetical mean roughness decreases by 40% with H2 (60%) addition. The X-ray diffraction peak intensity ratio [Cu(111)/Cu(200)] increases with H2 content, which indicates that the crystallinity of the Cu film has been improved. The property of Cu filling in the contact hole is much improved by H2 addition sputtering after low-temperature annealing (350 °C). Cu film was electroplated on the sputtered Cu. The roughness of the electroplated Cu surface does not depend on the roughness of the initial sputtered Cu surface even though H2 is added during Cu sputtering. However, the crystal orientation of the electroplated Cu film [(111)/(200) ratio] can be controlled by the crystal orientation of the seed sputtered Cu film; that is, H2 addition during Cu sputtering results in a good crystal orientation of the electroplated Cu film.