bluuebunny/crossref_metadata_2025 huggingface dataset:
Wave propagation in a duct with a periodic Helmholtz resonators array
Authors: Wang Xu , Mak Cheuk-Ming
Published: February 2012

Helmholtz resonator is often used to reduce noise in a narrow frequency range. To obtain a broader noise attenuation band, combing several resonators is a possible way. This paper presents a theoretical study of sound propagation in a one-dimensional duct with identical side-branch resonators mounted periodically. The analysis of each resonator was based on a distributed-parameter model that considered multi-dimensional wave propagation in its neck-cavity interface. This model provided a more accurate prediction of the resonant frequency of the resonator than traditional lumped-parameter model. Bloch wave theory and the transfer matrix method were used to investigate wave propagation in these spatially periodic resonators. The results predicted by the theory fit well with the computer simulation using a three-dimensional finite element method and the experimental results. This study indicates that the wave coupling in this periodic system results in the dispersion of the frequency band into the stop and the pass bands. The long-term significance is that periodic resonators may more effectively control noise in ducts by broadening the bandwidth they attenuate and increasing the magnitude of sound attenuation.
Multifunctional design of inertially-actuated velocity feedback controllers
Authors: Elliott S. J. , Rohlfing J. , Gardonio P.
Published: February 2012

The vibration of a structure can be controlled using either a passive tuned mass damper or using an active vibration control system. In this paper, the design of a multifunctional system is discussed, which uses an inertial actuator as both a tuned mass damper and as an element in a velocity feedback control loop. The natural frequency of the actuator would normally need to be well below that of the structure under control to give a stable velocity feedback controller, whereas it needs to be close to the natural frequency of a dominant structural resonance to act as an effective tuned mass damper. A compensator is used in the feedback controller here to allow stable feedback operation even when the actuator natural frequency is close to that of a structural mode. A practical example of such a compensator is described for a small inertial actuator, which is then used to actively control the vibrations both on a panel and on a beam. The influence of the actuator as a passive tuned mass damper can be clearly seen before the feedback loop is closed, and broadband damping is then additionally achieved by closing the velocity feedback loop.
Effect of cochlear implants on children’s perception and production of speech prosody
Authors: Nakata Takayuki , Trehub Sandra E. , Kanda Yukihiko
Published: February 2012

Japanese 5- to 13-yr-olds who used cochlear implants (CIs) and a comparison group of normally hearing (NH) Japanese children were tested on their perception and production of speech prosody. For the perception task, they were required to judge whether semantically neutral utterances that were normalized for amplitude were spoken in a happy, sad, or angry manner. The performance of NH children was error-free. By contrast, child CI users performed well below ceiling but above chance levels on happy- and sad-sounding utterances but not on angry-sounding utterances. For the production task, children were required to imitate stereotyped Japanese utterances expressing disappointment and surprise as well as culturally typically representations of crow and cat sounds. NH 5- and 6-year-olds produced significantly poorer imitations than older hearing children, but age was unrelated to the imitation quality of child CI users. Overall, child CI user’s imitations were significantly poorer than those of NH children, but they did not differ significantly from the imitations of the youngest NH group. Moreover, there was a robust correlation between the performance of child CI users on the perception and production tasks; this implies that difficulties with prosodic perception underlie their difficulties with prosodic imitation.
Contactless transport of matter in the first five resonance modes of a line-focused acoustic manipulator
Authors: Foresti Daniele , Nabavi Majid , Poulikakos Dimos
Published: February 2012

The first five resonance modes for transport of matter in a line-focused acoustic levitation system are investigated. Contactless transport was achieved by varying the height between the radiating plate and the reflector. Transport and levitation of droplets in particular involve two limits of the acoustic forces. The lower limit corresponds to the minimum force required to overcome the gravitational force. The upper limit corresponds to the maximum acoustic pressure beyond which atomization of the droplet occurs. As the droplet size increases, the lower limit increases and the upper limit decreases. Therefore to have large droplets levitated, relatively flat radiation pressure amplitude during the translation is needed. In this study, using a finite element model, the Gor’kov potential was calculated for different heights between the reflector and the radiating plate. The application of the Gor’kov potential was extended to study the range of droplet sizes for which the droplets can be levitated and transported without atomization. It was found that the third resonant mode (H3–mode) represents the best compromise between high levitation force and smooth pattern transition, and water droplets of millimeter radius can be levitated and transported. The H3–mode also allows for three translation lines in parallel.
Relationships of quantitative ultrasound parameters with cancellous bone microstructure in human calcaneus in vitro
Authors: Wear Keith A. , Nagaraja Srinidhi , Dreher Maureen L. , Gibson Sheng L.
Published: February 2012

Ultrasound parameters (attenuation, phase velocity, and backscatter), bone mineral density (BMD), and microarchitectural features were measured on 29 human cancellous calcaneus samples in vitro. Regression analysis was performed to predict ultrasound parameters from BMD and microarchitectural features. The best univariate predictors of the ultrasound parameters were the indexes of bone quantity: BMD and bone volume fraction (BV/TV). The most predictive univariate models for attenuation, phase velocity, and backscatter coefficient yielded adjusted squared correlation coefficients of 0.69–0.73. Multiple regression models yielded adjusted correlation coefficients of 0.74–0.83. Therefore attenuation, phase velocity, and backscatter are primarily determined by bone quantity, but multiple regression models based on bone quantity plus microarchitectural features achieve slightly better predictive performance than models based on bone quantity alone.
Maximum entropy approach to statistical inference for an ocean acoustic waveguide
Authors: Knobles D. P. , Sagers J. D. , Koch R. A.
Published: February 2012

A conditional probability distribution suitable for estimating the statistical properties of ocean seabed parameter values inferred from acoustic measurements is derived from a maximum entropy principle. The specification of the expectation value for an error function constrains the maximization of an entropy functional. This constraint determines the sensitivity factor (β) to the error function of the resulting probability distribution, which is a canonical form that provides a conservative estimate of the uncertainty of the parameter values. From the conditional distribution, marginal distributions for individual parameters can be determined from integration over the other parameters. The approach is an alternative to obtaining the posterior probability distribution without an intermediary determination of the likelihood function followed by an application of Bayes’ rule. In this paper the expectation value that specifies the constraint is determined from the values of the error function for the model solutions obtained from a sparse number of data samples. The method is applied to ocean acoustic measurements taken on the New Jersey continental shelf. The marginal probability distribution for the values of the sound speed ratio at the surface of the seabed and the source levels of a towed source are examined for different geoacoustic model representations.
Regime change and oscillation thresholds in recorder-like instruments
Authors: Auvray Roman , Fabre Benoît , Lagrée Pierre-Yves
Published: February 2012

Based on results from the literature, a description of sound generation in a recorder is developed. Linear and non-linear analysis are performed to study the dependence of the frequency on the jet velocity. The linear analysis predicts that the frequency is a function of the jet velocity. The non-linear resolution provides information about limit cycle oscillation and hysteretic regime change thresholds. A comparison of the frequency between linear theory and experiments on a modified recorder shows good agreement except at very low jet velocities. Although the predicted threshold for the onset of the first regime shows an important deviation from experiments, the hysteresis of threshold to higher regimes is accurately estimated. Furthermore, a qualitative analysis of the influence of different parameters in the model on the sound generation and regime changes is presented.
Response probability distribution of built-up vibro-acoustic systems
Authors: Reynders Edwin , Langley Robin S.
Published: February 2012

The vibro-acoustic response of built-up structures, consisting of stiff components with low modal density and flexible components with high modal density, is sensitive to small imperfections in the flexible components. In this paper, the uncertainty of the response is considered by modeling the low modal density master system as deterministic and the high modal density subsystems in a nonparametric stochastic way, i.e., carrying a diffuse wave field, and by subsequently computing the response probability density function. The master system’s mean squared response amplitude follows a singular noncentral complex Wishart distribution conditional on the subsystem energies. For a single degree of freedom, this is equivalent to a chi-square or an exponential distribution, depending on the loading conditions. The subsystem energies follow approximately a chi-square distribution when their relative variance is smaller than unity. The results are validated by application to plate structures, and good agreement with Monte Carlo simulations is found.
Re-expansion method for circular waveguide discontinuities: Application to concentric expansion chambers
Authors: Homentcovschi Dorel , Miles Ronald N.
Published: February 2012

The paper applies the re-expansion method for analyzing planar discontinuities at the junction of two axi-symmetrical circular waveguides. The normal modes in the two waveguides are expanded at the junction plane into a system of functions accounting for velocity singularities at the corner points. As the new expansion has a high convergence order, only a few terms have to be considered for obtaining the solution of most practical problems. This paper gives the equivalent impedance accounting for nonplanar waves into a plane-wave analysis and also the scattering matrix describing the coupling of arbitrary modes at each side of the discontinuity valid in the case of many propagating modes in both sides of the duct. The last section applies the re-expansion technique to some concentric expansion chambers providing an explicit formula for the transmission loss coefficient.
Conformal mapping for the Helmholtz equation: Acoustic wave scattering by a two dimensional inclusion with irregular shape in an ideal fluid
Authors: Liu Gang , Jayathilake Pahala G. , Khoo Boo Cheong , Han Feng , Liu Dian Kui
Published: February 2012

The complex variables method with mapping function was extended to solve the linear acoustic wave scattering by an inclusion with sharp/smooth corners in an infinite ideal fluid domain. The improved solutions of Helmholtz equation, shown as Bessel function with mapping function as the argument and fractional order Bessel function, were analytically obtained. Based on the mapping function, the initial geometry as well as the original physical vector can be transformed into the corresponding expressions inside the mapping plane. As all the physical vectors are calculated in the mapping plane (η,η¯), this method can lead to potential vast savings of computational resources and memory. In this work, the results are validated against several published works in the literature. The different geometries of the inclusion with sharp corners based on the proposed mapping functions for irregular polygons are studied and discussed. The findings show that the variation of angles and frequencies of the incident waves have significant influence on the bistatic scattering pattern and the far-field form factor for the pressure in the fluid.
Influence of acute hyperglycemia on otoacoustic emissions and the medial olivocochlear reflex
Authors: Jacobs Peter G. , Konrad-Martin Dawn , Mcmillan Garnett P. , McDermott Daniel , Fausti Stephen A. , Kagen David , Wan Eric A.
Published: February 2012

Stimulus-frequency (SF) otoacoustic emission (OAE) amplitude and the amplitude of medial olivocochlear (MOC) inhibition of SF OAEs for ipsilateral, contralateral and bilateral MOC reflex elicitors were recorded in six subjects with type 2 diabetes during a glucose tolerance test (GTT). Five of the six subjects were tested twice for a total of 11 trials and three subjects were tested in a control experiment. During the GTT experiment, the subjects’ blood glucose was elevated from a euglycemic level below 150 mg/dL to a hyperglycemic level above 160 mg/dL following the consumption of a bolus of 80 g of sugar. A subset of three subjects were tested in a control experiment during which SF OAE and MOC reflex measurements were made while blood sugar levels remained constant within the euglycemic region. Mean SF OAE amplitudes were elevated following glucose consumption. A statistically significant increase in MOC inhibition amplitude was observed during elevated sugar levels for the 11 GTT trials. Maximum inhibition occurred about an hour after glucose consumption when blood glucose levels peaked. Results indicate that acute hyperglycemia influences efferent control of the cochlea in people with type 2 diabetes.
Application of the Beilis–Tappert parabolic equation method to sound propagation over irregular terrain
Authors: Parakkal Santosh , Gilbert Kenneth E. , Di Xiao
Published: February 2012

The Beilis–Tappert (1979) parabolic equation method is attractive for irregular terrain because it treats surface variations in terms of a simple multiplicative factor (“phase screen”). However, implementing the exact sloping-surface impedance condition is problematic if one wants the computational efficiency of a Fourier parabolic equation algorithm. This article investigates an approximate flat-ground impedance condition that allows the Beilis–Tappert phase screen method to be used with a Fourier algorithm without any added complications. The exact sloping-surface impedance condition is derived and applied to propagation predictions over hills with maximum slopes from 5° to 22°. The predictions with the exact impedance condition are compared to predictions using the approximate flat-ground impedance condition. It is found that for slopes less than 15°–20°, the flat-ground impedance condition is sufficiently accurate. For slopes greater than approximately 20°, the limiting factor on numerical accuracy is not the flat-ground impedance approximation, but rather the narrow-angle approximation required by the Beilis–Tappert method. Thus, within the 20° limitation and using the flat-ground impedance condition with a Fourier parabolic equation, sound propagation over irregular terrain can be computed simply, efficiently, and accurately.
Maximum likelihood estimation of direction of arrival using an acoustic vector-sensor
Authors: Levin Dovid , Habets Emanuël A. P. , Gannot Sharon
Published: February 2012

A vector-sensor consisting of a monopole sensor collocated with orthogonally oriented dipole sensors is used for direction of arrival (DOA) estimation in the presence of an isotropic noise-field or internal device noise. A maximum likelihood (ML) DOA estimator is derived and subsequently shown to be a special case of DOA estimation by means of a search for the direction of maximum steered response power (SRP). The problem of SRP maximization with respect to a vector-sensor can be solved with a computationally inexpensive algorithm. The ML estimator achieves asymptotic efficiency and thus outperforms existing estimators with respect to the mean square angular error (MSAE) measure. The beampattern associated with the ML estimator is shown to be identical to that used by the minimum power distortionless response beamformer for the purpose of signal enhancement.
Spatial coherence and cross correlation of three-dimensional ambient noise fields in the ocean
Authors: Walker Shane C. , Buckingham Michael J.
Published: February 2012

Ambient acoustic noise fields in the ocean are generally three dimensional in that they exhibit vertical and horizontal directivity. A model of spatially homogeneous noise is introduced in which the directionality is treated as separable, that is, the overall directionality of the field is the product of the individual directivities in the horizontal and vertical. A uni-modal von Mises circular distribution from directional statistics is taken to represent the noise in the horizontal, whilst the vertical component is consistent with a surface distribution of vertical dipoles. An analysis of the coherence and cross correlation of the noise at two horizontally aligned sensors is developed. The coherence function involves a single integral over finite limits, whilst the cross-correlation function, derived on the assumption that the noise has been pre-whitened, is given by an integral with limits that depend on the correlation delay time. Although the cross-correlation function does not exhibit delta functions that could be identified with the Green’s function for propagation between the two sensors in the field, it does drop abruptly to zero at numerical time delays equal to the travel time between the sensors. Hence the noise could be used to recover the sound speed in the medium.
Viral and Inflammatory Triggers of Neurodegenerative Diseases
Authors: Deleidi Michela , Isacson Ole
Published: February 2012

Immune pathways and cytokines induced by viral infections can render neurons vulnerable to subsequent degeneration and may serve as therapeutic targets for neuroprotection.
Comment on “Rapid Cancer Detection by Topically Spraying a γ-Glutamyltranspeptidase–Activated Fluorescent Probe”
Authors: Shi Chunmeng
Published: February 2012

In contrast to the imaging agent described by Urano
et al
., near-infrared fluorescent probes can be used for targeted cancer theranostics without biochemical conjugation.
Response to Comment on “Rapid Cancer Detection by Topically Spraying a γ-Glutamyltranspeptidase–Activated Fluorescent Probe”
Authors: Kobayashi Hisataka , Choyke Peter L.
Published: February 2012

The development of imaging agents for cancer diagnostics and therapeutics can follow one of two pathways: bottom-up or top-down.
The Benefits of Culture
Authors: Smith Orla M.
Published: February 2012

Cultured neurons from induced pluripotent stem cells derived from Alzheimer’s disease patients rapidly recapitulate the pathological hallmarks of this disease.
Sleepless and Diabetic
Authors: Cheng Mickie H.
Published: February 2012

Rare variants in the melatonin receptor may explain an increased risk for type 2 diabetes.
Using Genomics to Get Rid of Pests
Authors: Nyendak Melissa
Published: February 2012

Researchers use a genomic approach to screen for new insecticides to prevent vector-borne disease.
How efficient can an emergency unit be? A perfect world model
Authors: Baboolal Kesh , Griffiths Jeff D , Knight Vincent A , Nelson Andrew V , Voake Cheryl , Williams Janet E
Published: February 2012

Various approaches have been used to identify possible routes for improvement of patient flow within an emergency unit (EU). One such approach is to use simulation to create a ‘real world’ model of an EU and carry out various tests to gauge ways of improvement. This paper proposes a novel approach in which simulation is used to create a ‘perfect world model’. The EU at a major UK hospital is modelled not as it is, but as it could be. The ‘efficiency gap’ between the ‘perfect world’ and the ‘real world’ demonstrates how operational research can be used effectively to identify the location of bottlenecks in the current ‘whole hospital’ patient pathway and can be used in the planning and managing of hospital resources to ensure the most effective use of those resources.
Can emergency care practitioners differentiate between an avoided emergency department attendance and an avoided admission?
Authors: Coates David , Rawstorne Steven , Benger Jonathan
Published: February 2012

Background

After a 999 call to the ambulance service, there is no ‘gold standard’ for determining whether the actions of an emergency care practitioner (ECP) result in a patient avoiding attendance at an emergency department (ED) or avoiding an admission to hospital. Within the Great Western Ambulance Service NHS Trust this outcome has previously been measured using an audit form completed by the ECP. However, the accuracy of the ECP's opinion has not been assessed.

Aim

To evaluate the accuracy of the ECP's opinion when deciding whether their actions resulted in a patient avoiding attendance at an ED or avoiding hospital admission.

Methods

Over a 10-week-period in 2009, quantitative data were collected using a case review approach. Anonymised patient consultation records were independently reviewed by an ED consultant and a general practitioner. The decision as to whether the actions of the ECP resulted in the patient avoiding ED attendance or hospital admission was compared between the three healthcare professionals using descriptive statistics and κ values to assess inter-rater agreement.

Results

Overall inter-rater agreement between the three healthcare professionals was κ=0.385 (fair agreement). The complete agreement rate on a case by case basis for all three healthcare professionals was 80.2% (138/172).

Conclusion

This study provides some evidence that ECPs can accurately report on whether their actions, at the time of that care episode, result in a patient avoiding attendance at an ED or avoiding a hospital admission.
Safety and efficacy of symptom-driven CT decision rule in fully conscious paediatric patients with symptoms after mild closed head trauma
Authors: Xiao Bo , Wu Fang-Fang , Zhang Hong , Ma Yan-Bin
Published: February 2012

Objects

The aim of the authors is to derive a safe, effective and feasible symptom-driven CT rule in fully conscious children ≥3 years with symptoms after head trauma, based on time-framed clinical course, radiological findings, outcome measures and prognosis of patients.

Methods

Fully conscious but symptomatic children ≥3 years after head injury (1997–2010) with CT performance ≤2 h since injury were included in the study. Additional exclusion criteria were set for patient selection. Evolution of clinical symptoms of patients in 24 h since injury was the focus in current study. Clinical data were extracted from standardised medical records on admission and observation charts.

Results

Data of 1897 eligible cases were retrospectively reviewed. Traumatic brain injury (TBI) was revealed radiologically in 73 cases (3.8%). Eight cases underwent surgery. Recursive partitioning analysis identified the following factors in the CT rule: any delayed headache commenced between 4 and 10 h since injury; significantly worsening headaches present between 2 and 12 h since injury; vomiting between 6 and 12 h since injury; and headache without significant changes persisted ≥12 h since injury. It has a sensitivity of 100% (95% CI 95.0% to 100.0%) and specificity of 72.1% (95% CI 70.0% to 74.1%) to predict cases with TBI.

Conclusions

A symptom-driven CT rule has been derived to identify cases at high risk of having TBI in fully conscious, but symptomatic children with mild closed head injury. To be practical, an additional observation rule is added.
The Manchester triage system: improvements for paediatric emergency care
Authors: van Veen Mirjam , Steyerberg Ewout W , van't Klooster Mariët , Ruige Madelon , van Meurs Alfred H J , van der Lei Johan , Moll Henriëtte A
Published: February 2012

Objective

To improve the Manchester Triage System (MTS) in paediatric emergency care.

Methods

The authors performed a prospective observational study at the emergency departments of a university and teaching hospital in The Netherlands and included children attending in 2007 and 2008. The authors developed and implemented specific age-dependent modifications for the MTS, based on patient groups where the system's performance was low. Nurses applied the modified system in 11 481 (84%) patients. The reference standard for urgency defined five levels based on a combination of vital signs at presentation, potentially life-threatening conditions, diagnostic resources, therapeutic interventions and follow-up. The reference standard for urgency was previously defined and available in 11 260/11 481 (96%) patients.

Results

Compared with the original MTS specificity improved from 79% (95% CI 79% to 80%) to 87% (95% CI 86% to 87%) while sensitivity remained similar ((63%, 95% CI 59% to 66%) vs (64%, 95% CI 60% to 68%)). The diagnostic OR increased (4.1 vs 11).

Conclusions

Modifications of the MTS for paediatric emergency care resulted in an improved specificity while sensitivity remained unchanged. Further research should focus on the improvement of sensitivity.
DNA DAMAGES AS A DEPOLYMERIZATION PROCESS
Authors: OCHOA JUAN G. DIAZ , WULKOW MICHAEL
Published: February 2012

The damage of DNA chains by environmental factors like radiation or chemical pollutants is a topic that has been frequently explored from an experimental and a theoretical perspective. Such damages, like the damage of the strands of a DNA chain, are toxic for the cell and can induce mutagenesis or apoptosis. Several models make strong assumptions for the distribution of damages; for instance a frequent supposition is that these damages are Poisson distributed. [L. Ma, J. J. Wagner, W. Hu, A. J. Levine and G. A. Stolovitzki, Proc. Natl. Acad. Sci.PNAS 102, 14266 (2005).] Only few models describe in detail the damage and the mechanisms associated to the formation and evolution of this damage distribution [H. Nikjoo, P. O'neill and D. T. Goodhead, Radiat. Res. 156, 577 (2001).] Nevertheless, such models do not include the repair processes which are continuously active inside the cell. In this work we present a novel model, based on a depolymerization process, describing the distribution of damages on DNA chains coupled to the dynamics associated to its repair processes. The central aim is not to give a final and comprehensive model, but a hint to represent in more detail the complex dynamics involved in the damage and repair of DNA. We show that there are critical parameters associated to this repair process, in particular we show how critical doses can be relevant in deciding whether the cell continues its repair process or starts apoptosis. We also find out that the damage concentration is related to the dose via a power law relation.
GROWTH AND CHARACTERIZATION OF NEW NONLINEAR OPTICAL SINGLE CRYSTALS OF 3-AMINOPHENOL ORTHOPHOSPHORIC ACID (3-AMPHPH)
Authors: RAJ K. RUSSEL , MURUGAKOOTHAN P.
Published: February 2012

The semi-organic 3-aminophenol-orthophosphoric acid (denoted as 3-amphph) single crystals were grown by slow evaporation solution technique with water as solvent. The resulted crystal has well-defined surface morphology and is transparent and colorless with a size of 29 × 17 × 4 mm3. The powder X-ray diffraction (XRD), NMR spectroscopic technique, UV-vis-NIR, TG/DTA and dielectric analysis are used to characterize the crystals. XRD analysis revealed that the crystal lattice of 3-amphph is orthorhombic having cell parameters a = 4.481(2) Å, b = 9.782(4) Å, c = 18.326(4) Å with non-centrosymmetric space group P 212121. Nonlinear optical studies indicated that the second harmonic generation (SHG) efficiency is 2.22 times that of the standard potassium dihydrogen phosphate (KDP) crystals. Growth mechanism and surface textures of the as-grown single crystals were analyzed by chemical etching analysis.
FRACTALS AND CHAOS RELATED TO ISING–ONSAGER–ZHANG LATTICES VERSUS THE JORDAN–VON NEUMANN–WIGNER PROCEDURES: QUATERNARY APPROACH
Authors: ŁAWRYNOWICZ JULIAN , NOWAK-KȨPCZYK MAŁGORZATA , SUZUKI OSAMU
Published: February 2012

The paper is inspired by a spectral decomposition and fractal eigenvectors for a class of piecewise linear maps due to Tasaki et al. [1994] and by an ad hoc explicit derivation of the Heisenberg uncertainty relation based on a Peano–Hilbert planar curve, due to El Nashie [1994]. It is also inspired by an elegant generalization by Zhang [2008] of the exact solution by Onsager [1944] to the problem of description of the Ising lattices [Ising, 1925]. This generalization involves, in particular, opening the knots by a rotation in a higher dimensional space and studying important commutators in the corresponding algebra. The investigations of Onsager and Zhang, involving quaternion matrices of order being a power of two, can be reformulated with the use of the "quaternionic" sequence of Jordan algebras implied by the fundamental paper of Jordan et al. [1934]. It is closely related to Heisenberg's approach to quantum theories, as summarized by him in his essay dedicated to Bohr on the occasion of Bohr's seventieth birthday (1955). We show that the Jordan structures are closely related to some types of fractals, in particular, fractals of the algebraic structure. Our study includes fractal renormalization and the renormalized Dirac operator, meromorphic Schauder basis and hyperfunctions on fractal boundaries, and a final discussion.
SEARCHING FOR SPECIFIC PERIODIC AND CHAOTIC OSCILLATIONS IN A PERIODICALLY-EXCITED HODGKIN–HUXLEY MODEL
Authors: SORIANO D. C. , ATTUX R. , SUYAMA R. , ROMANO J. M. T.
Published: February 2012

This work has a twofold aim: to present a numerical analysis of the Hodgkin–Huxley model in a nonsmooth excitation scenario — which is both challenging and theoretically relevant — and to use the established framework as a basis for testing a method to search for specific oscillating patterns in dynamical systems. The analysis is founded on classical qualitative methods — bifurcation diagrams, phase space and spectral analysis — and on the calculation of the system Lyapunov spectrum. This calculation is carried out by means of an algorithm particularly suited to deal with nonsmooth excitation and the complexity of the state equations. The obtained Lyapunov exponents are then used to build a robust cost function (invariant with respect to the initial conditions or specific trajectories in a given basin of attraction) for seeking predefined dynamical patterns that are optimized using the particle swarm optimization algorithm. This bioinspired method possesses two desirable features: it has a significant global search potential and does not demand cost function manipulation. The proposed approach, which was tested here in different representative scenarios for the Hodgkin–Huxley model, has a promising application potential in general dynamical contexts and can also be a valuable tool in the planning of drug administration and electrical stimulation of neuronal and cardiac cells.
MEASURABLE DYNAMICS ANALYSIS OF TRANSPORT IN THE GULF OF MEXICO DURING THE OIL SPILL
Authors: BOLLT ERIK M. , LUTTMAN AARON , KRAMER SEAN , BASNAYAKE RANIL
Published: February 2012

On April 20, 2010, an oil well cap explosion below the Deepwater Horizon, an off-shore oil rig in the Gulf of Mexico, started the worst human-caused submarine oil spill ever. Though an historic tragedy for the marine ecosystem, the unprecedented monitoring of the spill in real time by satellites and increased modeling of the natural oceanic flows has provided a wealth of data, allowing analysis of the flow dynamics governing the spread of the oil. In this work, we present the results of two computational analyses describing the mixing, mass transport, and flow dynamics of the oil dispersion in the Gulf of Mexico over the first 100 days of the spill. Transfer operator methods are used to determine the spatial partitioning of regions of homogeneous dynamics into almost-invariant sets, and Finite Time Lyapunov Exponents are used to compute pseudo-barriers to the mixing of the oil between these regions. The two methods give complementary results, generating a comprehensive description of the oil flow dynamics over time.
EXISTENCE OF EXACT FAMILIES OF TRAVELING WAVE SOLUTIONS FOR THE SIXTH-ORDER RAMANI EQUATION AND A COUPLED RAMANI EQUATION
Authors: LI JIBIN
Published: February 2012

By using the method of dynamical systems and the results in [Li & Zhang, 2011] to the sixth-order Ramani equation and a coupled Ramani equation, the families of exact traveling wave solutions can be obtained.
LINEAR CENTERS WITH PERTURBATIONS OF DEGREE 2d + 5
Authors: HUANG WENTAO , CHEN XINGWU , ROMANOVSKI VALERY G.
Published: February 2012

We describe a method for studying the center and isochronicity problems for a class of differential systems in the form of linear center perturbed by homogeneous series of degree 2d + m, where d is a non-negative real number and m is a positive integer. As an application, we classify centers and isochronous centers for a particular case when m = 5.
CHAOTIC AND NONCHAOTIC BEHAVIOR IN THREE-DIMENSIONAL QUADRATIC SYSTEMS: 5-1 DISSIPATIVE CASES
Authors: ZHANG FU , HEIDEL JACK
Published: February 2012

We show analytically that almost all three-dimensional dissipative quadratic systems of ordinary differential equations with a total of five terms on the right-hand side and one nonlinear term (namely 5-1 cases) are not chaotic except twenty one of them. Indeed we find nine systems that exhibit chaos, which were discovered by Sprott and Malasoma earlier. They are the simplest dissipative chaotic systems found so far. In this paper, we also extend Heidel–Zhang's theorem which provides sufficient conditions for solutions in the three-dimensional autonomous systems with polynomials and rational expressions on the right-hand side being nonchaotic. We then investigate the twenty one systems analytically and numerically. We show the portraits of some typical chaotic and nonchaotic solutions in phase space. For two of the systems that exhibit chaos we found stable period 1, 2, 4, 8 and 12 orbits numerically.
A MULTIVIBRATOR CIRCUIT BASED ON CHAOS GENERATION
Authors: CAMPOS-CANTÓN E. , FEMAT R. , BARAJAS-RAMÍREZ J. G. , CAMPOS-CANTÓN I.
Published: February 2012

We present a parameterized method to design multivibrator circuits via piecewise-linear (PWL) chaotic systems, which can exhibit double-scroll oscillations. The circuit is conformed exploiting a parametric modulation that manipulates the equilibrium stability of each linear subsystem. Chua's oscillator is used as benchmark to illustrate the effectiveness of the proposed method to design multivibrator circuits. Thus, our proposal allows the design of the three configurations of a multivibrator: monostable, astable, and bistable. Potential applications are illustrated designing a pulse generator and a full S-R flip flop device based on our all-in-one multivibrator circuit.
LOCALIZED OSCILLATIONS IN DIFFUSIVELY COUPLED CYCLIC NEGATIVE FEEDBACK SYSTEMS
Authors: LANZA VALENTINA , CORINTO FERNANDO , GILLI MARCO
Published: February 2012

Oscillations in networks composed of Cyclic Negative Feedback systems (CNF systems) are widely used to mimic many periodic phenomena occurring in systems biology. In particular, the possible coexistence of different attractors permits to suitably describe the differentiating processes arising in living cells. The aim of the manuscript is to characterize, through a spectral based technique, the complex global dynamical behaviors emerging in arrays of diffusively coupled CNF systems.
ON THE BOUNDNESS OF SOME SOLUTIONS OF THE LÜ SYSTEM
Authors: ZHANG FUCHEN , MU CHUNLAI , LI XIAOWU
Published: February 2012

By constructing a suitable Lyapunov function, we show that for the Lü chaotic system parameters in some specified regions, the solutions of the system are globally bounded.
ON THE NUMBER OF ZEROS OF ABELIAN INTEGRAL FOR A CUBIC ISOCHRONOUS CENTER
Authors: WU KUILIN , ZHAO YUNLIN
Published: February 2012

In this paper, we study the number of limit cycles that bifurcate from the periodic orbits of a cubic reversible isochronous center under cubic perturbations. It is proved that in this situation the least upper bound for the number of zeros (taking into account the multiplicity) of the Abelian integral associated with the system is equal to four. Moreover, for each k = 0, 1, …, 4, there are perturbations that give rise to exactly k limit cycles bifurcating from the period annulus.
A NEW ALGORITHM FOR COMPUTING ONE-DIMENSIONAL STABLE AND UNSTABLE MANIFOLDS OF MAPS
Authors: LI HUIMIN , FAN YANGYU , ZHANG JING
Published: February 2012

A new algorithm is presented to compute one-dimensional stable and unstable manifolds of fixed points for both two-dimensional and higher dimensional diffeomorphism maps. When computing the stable manifold, the algorithm does not require the explicit expression of the inverse map. The global manifold is grown from a local manifold and one point is added at each step. The new point is located with a "prediction and correction" scheme, which avoids searching the computed part of the manifold with a bisection method and accelerates the searching process. By using the fact that the Jacobian transports derivatives along the orbit of the manifold, the tangent component of the manifold is determined and a new accuracy criterion is proposed to check whether the new point that defines the manifold is acceptable. The performance of the algorithm is demonstrated with several numerical examples.
H∞ SYNCHRONIZATION OF SWITCHED CHAOTIC SYSTEMS AND ITS APPLICATION TO SECURE COMMUNICATIONS
Authors: WAN ZHANG-LIN , LIAO TEH-LU , HOU YI-YOU , YAN JUN-JUH
Published: February 2012

This paper deals with the H∞ synchronization problem of switched chaotic systems accompanied by a time-driven switching law and its application to secure communications. Based on the Lyapunov stability theory and linear matrix inequality (LMI) and linear matrix equality (LME) optimization techniques, an output feedback controller that guarantees the synchronization of switched master-slave chaotic systems is designed. A chaotic encryption technique that uses synchronization is proposed for securely transmitting a message over public channels. Numerical simulations of both analog and digital security communication systems are conducted to demonstrate the effectiveness of the proposed methods.
TWO-TO-ONE RESONANT HOPF BIFURCATIONS IN A QUADRATICALLY NONLINEAR OSCILLATOR INVOLVING TIME DELAY
Authors: JI J. C. , LI X. Y. , LUO Z. , ZHANG N.
Published: February 2012

The trivial equilibrium of a weakly nonlinear oscillator having quadratic nonlinearities under a delayed feedback control can change its stability via a single Hopf bifurcation as the time delay increases. Double Hopf bifurcation occurs when the characteristic equation has two pairs of purely imaginary solutions. An interaction of resonant Hopf–Hopf bifurcations may be possible when the two critical time delays corresponding to the two Hopf bifurcations have the same value. With the aid of normal form theory and centre manifold theorem as well as the method of multiple scales, the present paper studies the dynamics of a quadratically nonlinear oscillator involving time delay in the vicinity of the point of two-to-one resonances of Hopf–Hopf bifurcations. The ratio of the frequencies of two Hopf bifurcations is numerically found to be nearly equal to two. The two resonant Hopf bifurcations can generate two respective periodic solutions. Consequently, the centre manifold corresponding to these two solutions is determined by a set of four first-order differential equations under two-to-one internal resonances. It is shown that the amplitudes of the two bifurcating periodic solutions admit the trivial solution and two-mode solutions for the averaged equations on the centre manifolds. Correspondingly, the cumulative behavior of the original nonlinear oscillator exhibits the initial equilibrium and a quasi-periodic motion having two frequencies. Illustrative examples are given to show the unstable zero solution, stable zero solution, and stable two-mode solution of the nonlinear oscillator under the two-to-one resonant Hopf–Hopf interactions.
COMPLEX DYNAMICS OF A HAMILTONIAN SYSTEM UNDER IMPULSIVE CONTROL
Authors: JIANG GUIRONG , YANG QIGUI
Published: February 2012

In this paper, the dynamical behavior of a Hamiltonian system under impulsive control is discussed by both theoretical and numerical analyses. The existence and stability of its period-one and period-three solutions are obtained in virtue of a discrete map. The conditions of existence for flip bifurcation and Hopf bifurcation are further derived by using center manifold theorem and bifurcation theory. Three attracting invariant closed curves, surrounding three fixed points respectively, are investigated. Moreover, chaos in the sense of Marotto is rigorously proven. Finally, some detailed numerical results including periodic solutions, bifurcation diagrams, and chaotic attractors, are illustrated by examples, which are in good agreement with the theoretical analysis.
WAVELETS ASSOCIATED WITH NONUNIFORM MULTIRESOLUTION ANALYSIS ON POSITIVE HALF-LINE
Authors: MEENAKSHI  , MANCHANDA P. , SIDDIQI A. H.
Published: February 2012

Gabardo and Nashed have studied nonuniform multiresolution analysis based on the theory of spectral pairs in a series of papers, see Refs. 4 and 5. Farkov,3 has extended the notion of multiresolution analysis on locally compact Abelian groups and constructed the compactly supported orthogonal p-wavelets on L2(ℝ+). We have considered the nonuniform multiresolution analysis on positive half-line. The associated subspace V0 of L2(ℝ+) has an orthonormal basis, a collection of translates of the scaling function φ of the form {φ(x ⊖ λ)}λ∈Λ+ where Λ+ = {0, r/N} + ℤ+, N > 1 (an integer) and r is an odd integer with 1 ≤ r ≤ 2N - 1 such that r and N are relatively prime and ℤ+ is the set of non-negative integers. We find the necessary and sufficient condition for the existence of associated wavelets and derive the analogue of Cohen's condition for the nonuniform multiresolution analysis on the positive half-line.
Predicting Protein Interactions by Brownian Dynamics Simulations
Authors: Meng Xuan-Yu , Xu Yu , Zhang Hong-Xing , Mezei Mihaly , Cui Meng
Published: February 2012

We present a newly adapted Brownian-Dynamics (BD)-based protein docking method for predicting native protein complexes. The approach includes global BD conformational sampling, compact complex selection, and local energy minimization. In order to reduce the computational costs for energy evaluations, a shell-based grid force field was developed to represent the receptor protein and solvation effects. The performance of this BD protein docking approach has been evaluated on a test set of 24 crystal protein complexes. Reproduction of experimental structures in the test set indicates the adequate conformational sampling and accurate scoring of this BD protein docking approach. Furthermore, we have developed an approach to account for the flexibility of proteins, which has been successfully applied to reproduce the experimental complex structure from the structure of two unbounded proteins. These results indicate that this adapted BD protein docking approach can be useful for the prediction of protein-protein interactions.
Measurement and Model Validation of Nanofluid Specific Heat Capacity with Differential Scanning Calorimetry
Authors: O'Hanley Harry , Buongiorno Jacopo , McKrell Thomas , Hu Lin-wen
Published: February 2012

Nanofluids are being considered for heat transfer applications; therefore it is important to know their thermophysical properties accurately. In this paper we focused on nanofluid specific heat capacity. Currently, there exist two models to predict a nanofluid specific heat capacity as a function of nanoparticle concentration and material. Model I is a straight volume-weighted average; Model II is based on the assumption of thermal equilibrium between the particles and the surrounding fluid. These two models give significantly different predictions for a given system. Using differential scanning calorimetry (DSC), a robust experimental methodology for measuring the heat capacity of fluids, the specific heat capacities of water-based silica, alumina, and copper oxide nanofluids were measured. Nanoparticle concentrations were varied between 5 wt% and 50 wt%. Test results were found to be in excellent agreement with Model II, while the predictions of Model I deviated very significantly from the data. Therefore, Model II is recommended for nanofluids.
Rosiglitazone Affects Nitric Oxide Synthases and Improves Renal Outcome in a Rat Model of Severe Ischemia/Reperfusion Injury
Authors: Betz Boris , Schneider Reinhard , Kress Tobias , Schick Martin Alexander , Wanner Christoph , Sauvant Christoph
Published: February 2012

Background.Nitric oxide (NO)-signal transduction plays an important role in renal ischemia/reperfusion (I/R) injury. NO produced by endothelial NO-synthase (eNOS) has protective functions whereas NO from inducible NO-synthase (iNOS) induces impairment. Rosiglitazone (RGZ), a peroxisome proliferator-activated receptor (PPAR)-γagonist exerted beneficial effects after renal I/R injury, so we investigated whether this might be causally linked with NOS imbalance.Methods.RGZ (5 mg/kg) was administered i.p. to SD-rats (f) subjected to bilateral renal ischemia (60 min). Following 24 h of reperfusion, inulin- and PAH-clearance as well as PAH-net secretion were determined. Morphological alterations were graded by histopathological scoring. Plasma NOx-production was measured. eNOS and iNOS expression was analyzed by qPCR. Cleaved caspase 3 (CC3) was determined as an apoptosis indicator and ED1 as a marker of macrophage infiltration in renal tissue.Results.RGZ improves renal function after renal I/R injury (PAH-/inulin-clearance, PAH-net secretion) and reduces histomorphological injury. Additionally, RGZ reduces NOxplasma levels, ED-1 positive cell infiltration and CC3 expression. iNOS-mRNA is reduced whereas eNOS-mRNA is increased by RGZ.Conclusion.RGZ has protective properties after severe renal I/R injury. Alterations of the NO pathway regarding eNOS and iNOS could be an explanation of the underlying mechanism of RGZ protection in renal I/R injury.
Hölder Continuity of Solutions to Parametric Generalized Vector Quasiequilibrium Problems
Authors: Peng Z. Y.
Published: February 2012

By using a linear scalarization method, we establish sufficient
conditions for the Hölder continuity of the solution mappings to a parametric generalized
vector quasiequilibrium problem with set‐valued mappings. These results extend the
recent ones in the recent literature, (e.g., Li et al. (2009), Li et al. (2011)). Furthermore, two examples are given
to illustrate the obtained result.