bluuebunny/crossref_metadata_2025 huggingface dataset:
Long term clinical outcome and bleeding complications among hospital survivors with acute coronary syndromes
Authors: Wong P , Robinson A , Shaw S , Rodrigues E
Published: March 2006

Objective

To examine the 21 month clinical outcome and bleeding complications in hospital survivors with non-ST segment elevation acute coronary syndromes (NSTEACS) who were discharged with combined clopidogrel and aspirin anti-thrombotic therapy, and compare with those having ST segment elevation myocardial infarction (STEMI) who were discharged with aspirin alone.

Design

Observational study.

Setting

A large university hospital.

Patients

224 patients were admitted to hospital with either NSTEACS or STEMI, and survived to discharge between 1 October 2001 and 31 December 2002.

Main outcome measures

Cardiovascular death, total death, new myocardial infarction, unstable angina requiring hospitalisation, stroke or transient ischaemic attack, coronary revascularisation; and fatal, life threatening, major and minor bleeding over 21 months after discharge.

Results

Despite having no or small infarct (median maximum creatine kinase 155 v 1295 u/l; p<0.001) and taking more antianginal drugs, patients with NSTEACS had similar rates of cardiovascular death (9.5% v 8.3%; p = NS), new myocardial infarction (9.5% v 6.5%; p = NS) or unstable angina requiring hospitalisation (15.5% v 10.2%; p = NS) when compared with STEMI. Fatal, life threatening or major bleeding were <1% in both groups (p = NS); and minor bleeding occurred in 4.3% NSTEACS and 2.8% STEMI patients respectively (p = NS).

Conclusions

Patients with NSTEACS had a similar and unfavourable long term outcome when compared with STEMI. There was no difference in serious bleeding complications between both groups.
Role of computed tomography before lumbar puncture: a survey of clinical practice
Authors: Greig P R , Goroszeniuk D
Published: March 2006

Introduction

It is becoming increasingly common to request computed tomography (CT) to rule out space occupying lesions before lumbar puncture (LP), even in patients with no clinical signs. Imaging trends within a busy district general hospital in Oxfordshire, UK were analysed with results used to clarify when imaging should be considered mandatory.

Method

A retrospective six month sample was obtained comprising all adults considered for LP. Observed frequencies of abnormal examination findings compared with abnormal investigations were used to determine sensitivity, specificity, positive predictive, and negative predictive values to assess the validity of using a normal clinical examination as a basis for excluding CT.

Results

64 patients were considered for LP. In total, 58 patients underwent LP, with a single patient receiving two. After an abnormal CT scan, six patients did not undergo a planned LP. In all six of these cases subarachnoid haemorrhage was detected, and in all cases this was considered a probable diagnosis. In no case was an LP precluded by an unsuspected space occupying lesion. Neurological examination showed a sensitivity of 0.72 (0.52 to 0.93), specificity 0.78 (0.64 to 0.91), positive predictive value 0.61 (0.41 to 0.83), and negative predictive value 0.85 (0.73 to 0.97).

Discussion

The high sensitivity and negative predictive values support normal neurological examination as an effective predictor of normal CT scan. This permits the recommendation in cases where subarachnoid haemorrhage is not suspected, a CT scan can be avoided provided there are no abnormal findings on physical or fundoscopic examination.
Investigation and management of severe hyponatraemia in a hospital setting
Authors: Huda M S B , Boyd A , Skagen K , Wile D , van Heyningen C , Watson I , Wong S , Gill G
Published: March 2006

Aims

To evaluate the assessment and management of severe hyponatraemia in a large teaching hospital.

Methods

Inpatients with serum sodium <125 mmol/l were identified prospectively from a laboratory database over a six month period. Notes were examined and data extracted. Case notes were carefully reviewed retrospectively by a consultant endocrinologist with regard to accuracy of the diagnosis and the appropriateness of investigations and management.

Results

104 patients with a serum sodium <125 mmol/l were identified. Mean (SD) age was 69 (14), 52% were female, mean hospital stay was 16 (12) days, and overall mortality 27%. Adequate investigations were rarely performed. Only 28 (26%) had plasma osmolality measured, 29 (27%) urine osmolality, 11 (10%) urinary sodium, 8 (8%) plasma cortisol, and 2 (2%) a short Synacthen test. Comparing the “ward” and “specialist review” diagnoses, there were significant discrepancies for “no cause found” (49% v 27%, p<0.001), alcohol (6% v 11% p<0.01), and syndrome of inappropriate antidiuresis (20% v 32%, p = 0.001). Treatment was often illogical with significant management errors in 33%. These included fluid restriction and intravenous saline given together (4%) and fluid restriction in diuretic induced hyponatraemia (6%). Mortality was higher in the group with management errors (41% v 20% p = 0.002).

Conclusion

Severe hyponatraemia is a serious condition, but its investigation and evaluation is often inadequate. Some treatment patterns seem to be arbitrary and illogical, and are associated with higher mortality.
PRETRANSITIONAL HEAT CAPACITY NEAR THE LOWER CONSOLUTE POINT OF NONIONIC SURFACTANT SOLUTIONS
Authors: SHIN SUNG TAE
Published: March 2006

The results of precision heat capacity measurements near the lower consolute point in aqueous solutions of non-ionic surfactants n-dodecyl hexaethylene glycol monoether (C12E6), C10E6, and C12E8, are reported. These surfactants form homogeneous single phase micellar solutions below the lower consolute point, Tc. The pretransitional specific heat in the homogeneous phase below Tc is found to grow with temperature and exhibits a power-law divergence. Analysis of the data obtained for the three systems reveals that the specific heat exponent, α=-αR/(1-αR)≅0.5, gives credence to mean field behavior.
OBSERVATION OF PHASE SEPARATED La0.5Sr0.5MnO3 FILM
Authors: LI TONG , DU YONGSHENG , YAN HUI , YUD DUNBO
Published: March 2006

La 0.5 Sr 0.5 MnO 3 films on (001) LaAlO 3 were prepared by RF magnetron sputtering using powder target and were studied by SQUID and XPS. The XPS results show the formation of Mn 3+ and Mn 4+, indicating the coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) clusters. SQUID measurement of LSMO on LAO and Si also support an interaction between them at low temperatures, resulting in the shift of hysteresis loops. Large coercivities at low temperature can be attributed to the pinning of both FM and AFM clusters and small coercivities at high temperature to the depinning of both FM and AFM phases, resulting from the thermal motion at higher temperatures which help to overcome the energy barrier and change the magnetic alignments.
A COMPARATIVE STUDY OF THE HODGKIN–HUXLEY AND FITZHUGH–NAGUMO MODELS OF NEURON PULSE PROPAGATION
Authors: PHILLIPSON PAUL E. , SCHUSTER PETER
Published: March 2006

The four-dimensional Hodgkin–Huxley equations are considered as the prototype for description of neural pulse propagation. Their mathematical complexity and sophistication prompted a simplified two-dimensional model, the FitzHugh–Nagumo equations, which display many of the former's dynamical features. Numerical and mathematical analysis are employed to demonstrate that the FitzHugh–Nagumo equations can provide quantitative predictions in close agreement with the Hodgkin–Huxley equations. The two most important parameters of a neural pulse are its speed c(T) and pulse height v max (T) and so numerical computations of these quantities predicted by the Hodgkin–Huxley equations are given over the entire temperature range T for stability of a neural pulse. Similarly, the FitzHugh–Nagumo equations are parameterized by two dimensionless quantities: a which determines the dynamics of the pulse front, and b whose departure from zero tailors the front to form the resultant pulse. Parallel computations are presented for the FitzHugh–Nagumo pulse whose relative simplicity permits analytic determination to close approximation of the dimensionless speed θ(a, b) and pulse height V max (a, b). It is shown that the two models are numerically identified by scaling according to c = 4904 θ cm/sec and v max = 115 V max mV where the numbers are a consequence of the experimental parameter values inherent to the Hodgkin–Huxley equations. With this connection, at a given temperature the Hodgkin–Huxley speed and pulse height determine unique values for the two FitzHugh–Nagumo parameters a and b. Approximate analytic solution for θ(a, b) allows construction of a three-dimensional [a, b, θ] state plot upon which a unique ridge defines, as a function of temperature, the speed and associated pulse height predicted by the Hodgkin–Huxley equations. The generality of the state plot suggests its application to other conductance models. Comparison of the Hodgkin–Huxley with the FitzHugh–Nagumo models highlight the quantitative limitations of the latter in the region of the minimum characterizing the back portion of the pulse. To overcome this limitation would require analytic extension of the FitzHugh–Nagumo dynamics to higher dimensionality.
ANTICONTROL OF CHAOS FOR A CONTINUOUS-TIME TAKAGI–SUGENO FUZZY SYSTEM VIA LOCAL TIME-DELAY FEEDBACK
Authors: KIM TAEK RYONG , JOO YOUNG HOON , PARK JIN BAE , CHEN GUANRONG
Published: March 2006

In this paper, a simple and systematic control design method is proposed for making a continuous-time Takagi–Sugeno (T–S) fuzzy system chaotic. The concept of parallel distributed compensation is employed to determine the structure of a fuzzy controller from a T–S fuzzy model. The fuzzy controller makes the T–S fuzzy model, which could be stable or unstable, bounded and chaotic. The verification of chaos in the closed-loop T–S fuzzy system is done by the following procedure. First, we establish an asymptotically approximate relationship between a continuous-time T–S fuzzy system with time-delay and a discrete-time T–S fuzzy system. Then, we verify the chaos in the closed-loop T–S fuzzy system by applying the Marotto theorem to its associated discrete-time T–S fuzzy system. The generated chaos is in the sense of Li and Yorke. Two examples are given to show that this methodology is simple and effective for anticontrol of chaos for a continuous-time T–S fuzzy system.
MULTIPULSE SHILNIKOV ORBITS AND CHAOTIC DYNAMICS FOR NONLINEAR NONPLANAR MOTION OF A CANTILEVER BEAM
Authors: YAO MINGHUI , ZHANG WEI
Published: March 2006

The multipulse Shilnikov orbits and chaotic dynamics for the nonlinear nonplanar oscillations of a cantilever beam are studied in this paper for the first time. The cantilever beam studied here is subjected to a harmonic axial excitation and two transverse excitations at the free end. The nonlinear governing equations of nonplanar motion with parametric and external excitations are obtained. The Galerkin procedure is applied to the partial differential governing equations to obtain a two-degree-of-freedom nonlinear system under combined parametric and forcing excitations. The resonant case considered here is principal parametric resonance-1/2 subharmonic resonance for the first mode and fundamental parametric resonance-primary resonance for the second mode. The parametrically and externally excited system is transformed to the averaged equation by using the method of multiple scales. From the averaged equation, the theory of normal form is used to find their explicit formulas. Based on normal form obtained above, the dissipative version of the energy-phase method is utilized to analyze the multipulse global bifurcations and chaotic dynamics for the nonlinear nonplanar oscillations of the cantilever beam. The energy-phase method is further improved to ensure the equivalence of topological structure for the phase portraits. The analysis of global dynamics indicates that there exist the multipulse jumping orbits in the perturbed phase space of the averaged equation for the nonlinear nonplanar oscillations of the cantilever beam. These results show that the multipulse Shilnikov type chaotic motions can occur for the nonlinear nonplanar oscillations of the cantilever beam. Numerical simulations are given to verify the analytical predictions. It is also found from the results of numerical simulation in three-dimensional phase space that the multipulse Shilnikov type orbits exist for the nonlinear nonplanar oscillations of the cantilever beam.
SYMMETRIC PERIODIC ORBITS AND GLOBAL DYNAMICS OF TORI IN AN O(2) EQUIVARIANT SYSTEM: TWO-DIMENSIONAL THERMAL CONVECTION
Authors: NET MARTA , SÁNCHEZ JUAN
Published: March 2006

Numerical simulations of two-dimensional Boussinesq thermal convection in a long cylindrical annulus with radial gravity and heating are used to study the influence of the reflection and rotation symmetries of the system on the sequence of local and global bifurcations leading to complex time dependent behavior. From the results of the linear stability analysis of symmetric periodic orbits, it is shown how, via gluing bifurcations, some quasi-periodic flows recover, as sets, symmetries lost in previous bifurcations. It is also shown how the same mechanism gives rise to a temporal chaotic attractor consisting of random switches between the symmetry-conjugate quasi-periodic orbits. At higher Rayleigh numbers, a chaotic-drifting behavior is found when a circle of invariant tori loses stability. In addition, detailed information about the Floquet multipliers and eigenfunctions of the periodic orbits involved in this dynamics is supplied.
A KIND OF TWO-INPUT CNN WITH APPLICATION
Authors: CAI HUAN , MIN LEQUAN
Published: March 2006

This paper presents a kind of two-input Cellular Neural Network (CNN). This kind of CNN has three templates: A-template, B-template and C-template. The B-template and C-template are in charge of coupling two input images to be processed by the CNN equation. It is expected the new CNN may be used to process simultaneously two images. As an application of the CNN, a background replacement (BR) CNN is introduced. The BR CNN can replace the light colored background of a RBG image by another color image. Two computer simulation examples show that the BR CNN image processing can display animated drawing effects, and animated cartoons.
PERFORMANCE OF FREQUENCY-MODULATED DIFFERENTIAL-CHAOS-SHIFT-KEYING COMMUNICATION SYSTEM OVER MULTIPATH FADING CHANNELS WITH DELAY SPREAD
Authors: XIA YONGXIANG , TSE CHI K. , LAU FRANCIS C. M. , KOLUMBÁN GÉZA
Published: March 2006

Multipath performance is an important consideration for chaos-based communication systems. In this letter, the performance of the FM-DCSK communication system over multipath fading channels is evaluated by computer simulations. Both Rayleigh fading and Ricean fading are considered, and the low-pass equivalent model of the FM-DCSK system is used in the simulation. Based on this model, we analyze the bit error performance of the system and the effects of system parameters on the bit-error performance.
CHAOS AND DYNAMICS OF CYCLIC TRUCKING OF SIZE TWO
Authors: NAGATANI TAKASHI
Published: March 2006

We study dynamical behavior of a few trucks which shuttle between an origin and a destination repeatedly. One loads goods on to trucks at the origin and the truck unloads at the destination. We present the dynamical model for cyclic trucking. The model is described in terms of only one nonlinear map defined from the vector Ti(n), i = 1,2,…,N for N trucks where Ti(n) is the arrival time of truck i at the origin on trip n. The study is limited to the case of two trucks. We clarify the time variations of time headway and tour time for the truck schedule. The distinct dynamical states (the regular, periodic, and chaotic motions) are found by varying delay time T min and loading parameter Γ. It is shown that dynamical transitions occur among the regular, periodic and chaotic motions. In periodic and chaotic motions, the tour time of trucks fluctuates highly and the carrying goods vary the tour time accordingly.
THE COMPUTATION OF LYAPUNOV EXPONENTS FOR PERIODIC TRAJECTORIES
Authors: HONG JIALIN
Published: March 2006

We present a new method for the numerical computation of Lyapunov exponents of periodic trajectories which is crucial in the investigation of dynamics. The computational time of this method is merely a period of the periodic trajectory considered, when Lyapunov exponents can be approximated as precise as one wants. Our method stems from a combination between Floquet theory on periodic linear differential systems and Lie group methods in structure preserving algorithms on manifolds. The Lyapunov exponents of a periodic trajectory of the Lorenz system and a periodic solitary wave of the nonlinear Schrödinger equation with periodic coefficients are investigated by using the method.
UNUSUAL CHAOTIC ATTRACTORS IN NONSMOOTH DYNAMIC SYSTEMS
Authors: GALVANETTO U.
Published: March 2006

The present paper describes an unusual example of chaotic motion occurring in a nonsmooth mechanical system affected by dry friction. The mechanical system generates one-dimensional maps the orbits of which seem to exhibit sensitive dependence on initial conditions only in an extremely small set of their field of definition. The chaotic attractor is composed of zones characterized by very different rates of divergence of nearby orbits: in a large portion of the chaotic attractor the system motion follows a regular pattern whereas the more usual irregular motion affects only a small portion of the attractor. The irregular phase reintroduces the orbit in the regular zone and the sequence is repeated. The Lyapunov exponent of the map is computed to characterize the steady state motions and confirm their chaotic nature.
SPONTANEOUS FORMATION OF MULTIARMED SPIRAL WAVES IN VARIOUS SIMPLE MODELS OF WEAKLY EXCITABLE MEDIA
Authors: ZARITSKI ROMAN M. , JU JINHYO , ASHKENAZI IRINA
Published: March 2006

We investigate a spontaneous formation of stable multiarmed spirals in two-dimensional excitable media, an effect observed in various biological and chemical systems. A previous study based on FitzHugh–Nagumo-type Pushchino model reported a robust effect of stable two- and three-armed spiral formation from nearby vortices, when the spirals rotate around unexcited cores, i.e. when excitability of the medium is low. In this study, we used a powerful parallel computer cluster to perform an extensive parameter search in two other widely used FitzHugh–Nagumo-type models, as well as in the two-component Oregonator model. We observed formation of stable n-armed spirals, with 2 ≤ n ≤ 10, whenever the excitability of the medium was sufficiently low. Thus, we conclude that the formation and persistence of stable multiarmed spirals (MAS) is not an artifact of one particular model, but, rather, it is an amazing higher-level self-organization property of a generic weakly excitable medium. We also establish quantitatively that such multiarmed spirals serve as high-frequency wave sources — a finding that has a direct relevance to cardiac defibrillation research.
ANALYSIS OF CHAOTIC INSTABILITIES IN A ROTATING BODY WITH INTERNAL ENERGY DISSIPATION
Authors: MEEHAN P. A. , ASOKANTHAN S. F.
Published: March 2006

Melnikov's method is used to analytically predict the onset of chaotic instability in a rotating body with internal energy dissipation. The model has been found to exhibit chaotic instability when a harmonic disturbance torque is applied to the system for a range of forcing amplitude and frequency. Such a model may be considered to be representative of the dynamical behavior of a number of physical systems such as a spinning spacecraft. In spacecraft, disturbance torques may arise under malfunction of the control system, from an unbalanced rotor, from vibrations in appendages or from orbital variations. Chaotic instabilities arising from such disturbances could introduce uncertainties and irregularities into the motion of the multibody system and consequently could have disastrous effects on its intended operation. A comprehensive stability analysis is performed and regions of nonlinear behavior are identified. Subsequently, the closed form analytical solution for the unperturbed system is obtained in order to identify homoclinic orbits. Melnikov's method is then applied on the system once transformed into Hamiltonian form. The resulting analytical criterion for the onset of chaotic instability is obtained in terms of critical system parameters. The sufficient criterion is shown to be a useful predictor of the phenomenon via comparisons with numerical results. Finally, for the purposes of providing a complete, self-contained investigation of this fundamental system, the control of chaotic instability is demonstated using Lyapunov's method.
CHIMERA STATES IN A RING OF NONLOCALLY COUPLED OSCILLATORS
Authors: ABRAMS DANIEL M. , STROGATZ STEVEN H.
Published: March 2006

Arrays of identical limit-cycle oscillators have been used to model a wide variety of pattern-forming systems, such as neural networks, convecting fluids, laser arrays and coupled biochemical oscillators. These systems are known to exhibit rich collective behavior, from synchrony and traveling waves to spatiotemporal chaos and incoherence. Recently, Kuramoto and his colleagues reported a strange new mode of organization — here called the chimera state — in which coherence and incoherence exist side by side in the same system of oscillators. Such states have never been seen in systems with either local or global coupling; they are apparently peculiar to the intermediate case of nonlocal coupling. Here we give an exact solution for the chimera state, for a one-dimensional ring of phase oscillators coupled nonlocally by a cosine kernel. The analysis reveals that the chimera is born in a continuous bifurcation from a spatially modulated drift state, and dies in a saddle-node collision with an unstable version of itself.
ON COMPUTATION OVER CHAOS USING NEURAL NETWORKS: APPLICATION TO BLIND SEARCH AND RANDOM NUMBER GENERATION
Authors: NETO JOÃO PEDRO , FERREIRA ADEMAR , COELHO HELDER
Published: March 2006

This paper deals with computation over dynamical analog systems, exploring applications of chaos. The dynamical system used is an artificial neural network model that can code any symbolic algorithm. Herein, we propose the integration of chaotic dynamics onto this model, to implement computational tasks, namely, a blind search algorithm and a pseudo-random number generator.
DELAY FEEDBACK CONTROL FOR INTERACTION OF HOPF AND PERIOD DOUBLING BIFURCATIONS IN DISCRETE-TIME SYSTEMS
Authors: WEN GUILIN , WANG QING-GUO , CHIU MIN-SEN
Published: March 2006

Interaction of Hopf and period doubling bifurcations, as a so-called codimension two singularity, may give rise to rich bifurcation outcomes depending on the two-parameter unfolding at the bifurcation point. In this paper, we develop a nonlinear delay control for interaction of Hopf and period doubling bifurcations at a desired parameter location with preferred bifurcation properties. For its linear control term, the gains are determined by the bifurcation critical conditions and are used to create this type of bifurcations at a desired parameter location. For its nonlinear control term, the gains are derived by the center manifold theorem and theory of normal form. They determine the type and stability of bifurcation solutions. The proposed control method is applicable to any uncontrolled system which can be stable, unstable or even chaotic. Numerical experiments verify the feasibility of the control methodology and clearly show easy manipulation of all kinds of possible solutions of the created bifurcation.
HORSESHOE CHAOS IN CELLULAR NEURAL NETWORKS
Authors: YANG XIAO-SONG , LI QINGDU
Published: March 2006

In this paper, we demonstrate chaos in low dimensional cellular neural networks for some weight matrices. To verify chaoticity of the dynamics in these cellular neural networks, we consider a cross-section properly chosen for the attractors obtained and study the dynamics of the corresponding Poincaré maps, and rigorously verify the existence of horseshoe in the manner of computer-assisted proof arguments.
STATIONARY SOLUTIONS ANALYSIS OF CELLULAR NEURAL NETWORKS
Authors: KE YUNQUAN
Published: March 2006

A class of cellular neural networks, containing the input and output terms, is investigated in this paper. The input and output synaptic weights are taken as the parameter in conjunction with the thresholds, and parameter spaces are constructed from them. Based on geometrical method, the parameter spaces are decomposed into many finite regions, and the value assignment range of stationary solutions is given when system parameters are determined on some regions.
PLANE MAPS, SINGULARITIES AND QUASI-FIXED POINTS
Authors: FISCHER P. , GILLIS D.
Published: March 2006

This work investigates maps T of the plane with points p ∈ ℝ2 where T is undefined. Through the study of certain families with a singularity at the origin two very different dynamics will be illustrated. The first example will show that a singularity has no apparent effect on forward mapping. In this example there exists also an attractive fixed point. The second example will illustrate a singularity that exhibits attracting fixed point-like behavior.
RECONSTRUCTION OF NONSTATIONARY SIGNALS ALONG THE WAVELET RIDGES
Authors: ÖZKURT NALAN , SAVACI F. ACAR
Published: March 2006

In this paper, the nonstationary signals have been recovered using the skeleton along the wavelet ridges in the noisy case and the attractors of the cleaned signals are reconstructed in the phase space by time-delay embedding. In order to verify the signal recovery and reconstruction procedure, the similarity measure Hausdorff distance between cleaned, noise-free original attractors have been calculated. The computations show that the procedure reduces the noise level acceptably and the reconstructed attractors are more similar to the original attractors.
A SUBTHRESHOLD ANALOG MOS CIRCUIT FOR LOTKA–VOLTERRA CHAOTIC OSCILLATOR
Authors: ASAI TETSUYA , KAMIYA TAISHI , HIROSE TETSUYA , AMEMIYA YOSHIHITO
Published: March 2006

We fabricated an analog integrated circuit (IC) that implements the Lotka–Volterra (LV) chaotic oscillator presented by Mimura and Kan-on [1986]. The LV system describes periodic or chaotic behaviors in prey–predator systems in simple mathematical form, and is suitable for analog IC implementation [Asai et al., 2003]. The proposed circuit consists of a small number of metal-oxide-semiconductor field-effect transistors (MOS FETs) operating in their subthreshold region. A new scaling factor of system variables, which was not discussed in [Asai et al., 2003], is also introduced for quantitative studies of designing practical hardware LV systems.
DIRECT DYNAMICS INVESTIGATION ON MECHANISM OF REACTION BETWEEN TRICHLORIDE AND H RADICAL
Authors: QI YAN , CHEN XIAO-FANG , HAN KE-LI
Published: March 2006

Direct dynamics within the framework of DFT has been used to study the reaction between Boron trichloride and H radical. Two sets of trajectories amounting to a total of 40 were simulated for different collision sites and initial velocities. Two reactive channels have been found. One is a Cl atom abstraction channel and the other is a Cl atom elimination channel. The detailed mechanisms of both reactive channels were depicted by sampling trajectories. For the first channel, the reaction mechanism proposed by ab initio calculations was represented. For the second channel, transition state was mapped out after the dynamics simulation.
METAL ION-LIGAND INTERACTION: HSAB PRINCIPLE VERSUS NBO AND AIM VIEW POINTS
Authors: MOHAJERI AFSHAN , ABASI MARYAM
Published: March 2006

Ab initio calculations were performed to study the applicability and reliability of the semi quantitative model based on the local hard-soft acid-base principle in studying the interaction of metal ions with ligands. The particular attention is devoted to the interaction of CO , CN-and SCN-as the base with some hard metal ions ( Li+, Na+, K+) and some soft metal ions ( Pd+2, Ag+2, Cd+2) as acids. The interaction energies were calculated using the HSAB principle and compared with the values obtained by the conventional MP2 method. The results show that the HSAB principle does not work in many cases and it fails to predict correct values for interaction energies. The AIM and NBO analyses were also performed to characterize the nature of the metal ion-ligand interaction. It is found that the charge transfers have great significance in the interaction of metal ions with ligands.
DFT METHOD STUDY ON LUBRICANT PROPERTIES OF DISULFIDE COMPOUNDS AS EXTREME PRESSURE ADDITIVE
Authors: WANG XUE-YE , LI XIN-FANG , WEN XIAO-HONG , TAN YUAN-QIANG
Published: March 2006

The molecular geometries optimization and electronic structures of fourteen disulfide compounds had been investigated by density functional theory (DFT) at 6-31G basis set level. The active atoms and active bonds of tribochemical reaction were obtained according to frontier molecular orbital theory, and the interaction energy of chemical adsorption between disulfides and metal surfaces were calculated. The structure-property relationship had been discussed with satisfactory results. The calculated results indicated that the S–S bond and C–S bond of compounds are trended to be broken when organic disulfide compounds interact with a metal, and the order of anti-wear properties for disulfide compounds: diphenyldisulfide >dibenzyldisulfide >di-n-dodecyldisulfide >di-n-octyldisulfide >di-n-butyldisulfide >diethyldisulfide, the extreme pressure properties of DBDS is superior to that of DPDS. The predicted results based on quantum chemical calculations are in excellent agreement with friction and wear test results.
STRUCTURES AND ELECTRONIC PROPERTIES OF MONOMER, DIMER AND TETRAMER OF LACTOSE REPRESSOR PROTEIN: MOLECULAR MECHANICS, MOLECULAR DYNAMICS, MOLECULAR ORBITAL AND CHARGE EQUILIBRATION CALCULATIONS
Authors: KURITA NORIYUKI , MATSUOKA MAKOTO , SENGOKU YASUO
Published: March 2006

Tetramer of lactose repressor (LacR) protein plays an essential role in controlling the transcription of DNA. The previous experimental studies elucidated that the carboxyl-terminal domain of LacR is important for the tetramerization of LacR. In the present study, we investigated stable structures of monomers, dimers and tetramer of LacR by molecular mechanics and molecular dynamics simulations, based on AMBER force field to elucidate the effect of the tetramerization domain on LacR structure. The obtained stable structures for both the LacR tetramers, with and without the tetramerization domain, indicate that this domain is essential for constructing a compact structure of LacR tetramer. On the other hand, this domain does not affect the structure of LacR dimer. Furthermore, we investigated the charge distributions and binding energies for these stable structures by the charge equilibration and semiempirical molecular orbital methods. The results elucidate how the removal of the tetramerization domain causes the change in the electrostatic interaction between LacR dimers in the LacR tetramer, resulting in the separation of LacR dimers without the domain.
RESPONSE OF ENERGY LEVELS AND WAVEFUNCTIONS OF 2-D ARTIFICIAL ATOMS TO CHANGES IN PARAMETERS IN THE HAMILTONIAN
Authors: GHOSH MANAS , HAZRA RAM KUNTAL , BHATTACHARYYA S. P.
Published: March 2006

We explore the pattern of evolution of energy levels and wavefunctions in a harmonically confined single electron artificial atom in 2 dimensions, in the presence of a perpendicular magnetic field and anharmonic perturbations. A configuration interaction (CI) type of approach in a basis of appropriate harmonic oscillator eigenfunctions is used, leading to a complex sparse hermitian matrix eigenvalue problem. We show that for a given strength of the confining potential descriptors like quantum information entropy, level spacing distribution, degree of localization of one electron density and probability current point to a threshold value for the cyclotron frequency (ωc), beyond which there appears to be a transition from a delocalized description rather than a localized one. No signature of quantum chaos is detected.
RECENT DEVELOPMENT IN THE STUDY OF SN2 REACTIONS AT HETEROATOMS AND ION PAIR SYSTEMS
Authors: REN YI , CHU SAN-YAN
Published: March 2006

Present review outlines the experimental and theoretical studies on the SN 2 reactions at heteroatoms ( N , O and S ) and ion pair systems in recent years, especially introduce research carried out at our group in detail. The similarities and differences between SN 2 at heteroatoms and at carbon are discussed. Some new structure–energy relationships were proposed. The accuracy of various theoretical schemes for calculating potential energy surfaces has been assessed.
Harnessing the Expert Knowledge of Older Workers: Issues and Challenges
Authors: Joe Carmel , Yoong Pak
Published: March 2006

This paper reports part of a study that examines how to harness the expert knowledge of older workers. Five older workers, from both public and private sector organisations, were interviewed face to face regarding their potential contributions to other colleagues based on their expertise on work practices. Preliminary results revealed the following set of issues and challenges: (a) challenges in transitioning to retirement; (b) relevant and transferable skills and knowledge; (c) organisational readiness in retaining knowledge and skills; and (d) the use of information technology to support knowledge sharing. The implications of these findings for future research will be discussed.
Thermal sensitivity of isolated vagal pulmonary sensory neurons: role of transient receptor potential vanilloid receptors
Authors: Ni Dan , Gu Qihai , Hu Hong-Zhen , Gao Na , Zhu Michael X. , Lee Lu-Yuan
Published: March 2006

A recent study has demonstrated that increasing the intrathoracic temperature from 36°C to 41°C induced a distinct stimulatory and sensitizing effect on vagal pulmonary C-fiber afferents in anesthetized rats ( J Physiol 565: 295–308, 2005). We postulated that these responses are mediated through a direct activation of the temperature-sensitive transient receptor potential vanilloid (TRPV) receptors by hyperthermia. To test this hypothesis, we studied the effect of increasing temperature on pulmonary sensory neurons that were isolated from adult rat nodose/jugular ganglion and identified by retrograde labeling, using the whole cell perforated patch-clamping technique. Our results showed that increasing temperature from 23°C (or 35°C) to 41°C in a ramp pattern evoked an inward current, which began to emerge after exceeding a threshold of ∼34.4°C and then increased sharply in amplitude as the temperature was further increased, reaching a peak current of 173 ± 27 pA ( n = 75) at 41°C. The temperature coefficient, Q10, was 29.5 ± 6.4 over the range of 35–41°C. The peak inward current was only partially blocked by pretreatment with capsazepine (Δ I = 48.1 ± 4.7%, n = 11) or AMG 9810 (Δ I = 59.2 ± 7.8%, n = 8), selective antagonists of the TRPV1 channel, but almost completely abolished (Δ I = 96.3 ± 2.3%) by ruthenium red, an effective blocker of TRPV1–4 channels. Furthermore, positive expressions of TRPV1–4 transcripts and proteins in these neurons were demonstrated by RT-PCR and immunohistochemistry experiments, respectively. On the basis of these results, we conclude that increasing temperature within the normal physiological range can exert a direct stimulatory effect on pulmonary sensory neurons, and this effect is mediated through the activation of TRPV1, as well as other subtypes of TRPV channels.
Role of purinergic cotransmission in the sympathetic control of arterial pressure variability in conscious rats
Authors: Emonnot Léa , Bakhos Charles , Chapuis Bruno , Oréa Valérie , Barrès Christian , Julien Claude
Published: March 2006

Previous studies have shown that the sympathetically mediated oscillations of arterial pressure (AP), the so-called Mayer waves, are shifted from 0.4 to 0.6 Hz after acute α-adrenoceptor blockade in conscious rats. This raises the possibility that, under physiological conditions, Mayer waves are mediated by the conjoint action of norepinephrine and other sympathetic cotransmitters. To evaluate the possible role of the cotransmitter ATP in determining the frequency of Mayer waves, AP and renal sympathetic nerve activity (RSNA) were simultaneously recorded in 10 conscious rats with cardiac autonomic blockade before and after acute blockade of P2 receptors with pyridoxal phosphate-6-azophenyl-2′,4′-disulfonic acid. P2 receptor blockade did not alter the mean level and overall variability of AP and RSNA but shifted peak coherence between AP and RSNA from 0.43 ± 0.02 to 0.22 ± 0.01 Hz. A model of the sympathetic limb of the arterial baroreceptor reflex was designed to simulate Mayer waves at 0.2 and 0.6 Hz, with norepinephrine and ATP, respectively, acting as the sole sympathetic cotransmitter. When both cotransmitters acted in concert, a single oscillation was observed at 0.4 Hz when the gain ratio of the adrenergic to the purinergic components was set at 15. The model thus accounted for an important role for ATP in determining Mayer wave frequency, but not in sustaining the mean level of AP or controlling its overall variability.
Cerebral hemodynamics during orthostatic stress assessed by nonlinear modeling
Authors: Mitsis Georgios D. , Zhang Rong , Levine Benjamin D. , Marmarelis Vasilis Z.
Published: March 2006

The effects of orthostatic stress, induced by lower body negative pressure (LBNP), on cerebral hemodynamics were examined in a nonlinear context. Spontaneous fluctuations of beat-to-beat mean arterial blood pressure (MABP) in the finger, mean cerebral blood flow velocity (MCBFV) in the middle cerebral artery, as well as breath-by-breath end-tidal CO2concentration (PetCO2) were measured continuously in 10 healthy subjects under resting conditions and during graded LBNP to presyncope. A two-input nonlinear Laguerre-Volterra network model was employed to study the dynamic effects of MABP and PetCO2changes, as well as their nonlinear interactions, on MCBFV variations in the very low (VLF; below 0.04 Hz), low (LF; 0.04–0.15 Hz), and high frequency (HF; 0.15–0.30 Hz) ranges. Dynamic cerebral autoregulation was described by the model terms corresponding to MABP, whereas cerebral vasomotor reactivity was described by the model PetCO2terms. The nonlinear model terms reduced the output prediction normalized mean square error substantially (by 15–20%) and had a prominent effect in the VLF range, both under resting conditions and during LBNP. Whereas MABP fluctuations dominated in the HF range and played a significant role in the VLF and LF ranges, changes in PetCO2accounted for a considerable fraction of the VLF and LF MCBFV variations, especially at high LBNP levels. The magnitude of the linear and nonlinear MABP-MCBFV Volterra kernels increased substantially above −30 mmHg LBNP in the VLF range, implying impaired dynamic autoregulation. In contrast, the magnitude of the PetCO2-MCBFV kernels reduced during LBNP at all frequencies, suggesting attenuated cerebral vasomotor reactivity under dynamic conditions. We speculate that these changes may reflect a progressively reduced cerebrovascular reserve to compensate for the increasingly unstable systemic circulation during orthostatic stress that could ultimately lead to cerebral hypoperfusion and syncope.
Adaptations in human neuromuscular function following prolonged unweighting: I. Skeletal muscle contractile properties and applied ischemia efficacy
Authors: Clark Brian C. , Fernhall Bo , Ploutz-Snyder Lori L.
Published: March 2006

Strength loss following disuse may result from alterations in muscle and/or neurological properties. In this paper, we report our findings on human plantar flexor muscle properties following 4 wk of limb suspension (unilateral lower limb suspension), along with the effect of applied ischemia (Isc) on these properties. In the companion paper (Part II), we report our findings on the changes in neurological properties. Measurements of voluntary and evoked forces, the compound muscle fiber action potential (CMAP), and muscle cross-sectional area (CSA) were collected before and after 4 wk of unilateral lower limb suspension in adults ( n = 18; 19–28 yr). A subset of subjects ( n = 6) received applications of Isc 3 days/wk (3 sets; 5-min duration). In the subjects not receiving Isc, the loss in CSA and strength was as expected (∼9 and 14%). We observed a 30% slowing in the duration of the CMAP, a 10% decrease in evoked doublet force, a 12% increase in the twitch-to-doublet force ratio, and an altered postactivation potentiation response (11% increase in the postactivation potentiation-to-doublet ratio). We also detected a 10% slowing in the ability of the plantar flexor to develop force during the initial phase of an evoked contraction, along with a 6% reduction in in vivo specific doublet force. In the Isc subjects, no preservation was observed in strength or the evoked muscle properties. However, the Isc group did maintain CSA of the lateral gastrocnemius, as the control subjects’ lateral gastrocnemius atrophied 10.2%, whereas the subjects receiving Isc atrophied 4.7%. Additionally, Isc abolished the unweighting-induced slowing in the CMAP. These findings suggest that unweighting alters the contractile properties involved in the excitation-contraction coupling processes and that Isc impacts the sarcolemma.
Adaptations in human neuromuscular function following prolonged unweighting: II. Neurological properties and motor imagery efficacy
Authors: Clark Brian C. , Manini Todd M. , Bolanowski Stanley J. , Ploutz-Snyder Lori L.
Published: March 2006

Strength loss following disuse may result from alterations in muscle and/or neurological properties. In this paper, we report our findings on human plantar flexor neurological properties following 4 wk of limb suspension [unilateral lower limb suspension (ULLS)], along with the effect of motor imagery (MI) training on these properties. In the companion paper (Part I), we report our findings on the changes in skeletal muscle properties. Additionally, in the present paper, we analyze our findings to determine the relative contribution of neural and muscular factors in strength loss. Measurements of central activation, the H-reflex, and nerve conduction were made before and after 4 wk of ULLS ( n = 18; 19–28 yr). A subset of the subjects ( n = 6) performed PF MI training 4 days/wk. Following ULLS, we observed a significant increase in the soleus H-reflex (45.4 ± 4.0 to 51.9 ± 3.7% expressed relative to the maximal muscle action potential). Additionally, there were longer intervals between the delivery of an electrical stimulus to the tibial nerve and the corresponding muscle action potential (M-wave latency; mean prolongation 0.49 ms) and H-reflex wave (H-wave latency; mean prolongation 0.46 ms). The efficacy of MI on strength was ambiguous, with no significant effect detected (although a modest effect size was observed; η2= 0.18). These findings suggest that unweighting induces plastic changes in neural function that appear to be spatially distributed throughout the nervous system. In terms of the relative contribution of neural and muscular factors regulating strength loss, we observed that neural factors (primarily deficits in central activation) explained 48% of the variability in strength loss, whereas muscular factors (primarily sarcolemma function) explained 39% of the variability.
Effect of temperature on skeletal muscle energy turnover during dynamic knee-extensor exercise in humans
Authors: Ferguson R. A. , Krustrup P. , Kjær M. , Mohr M. , Ball D. , Bangsbo J.
Published: March 2006

The present study examined the effect of elevated temperature on muscle energy turnover during dynamic exercise. Nine male subjects performed 10 min of dynamic knee-extensor exercise at an intensity of 43 W (SD 10) and a frequency of 60 contractions per minute. Exercise was performed under normal (C) and elevated muscle temperature (HT) through passive heating. Thigh oxygen uptake (V̇o2) was determined from measurements of thigh blood flow and femoral arterial-venous differences for oxygen content. Anaerobic energy turnover was estimated from measurements of lactate release as well as muscle lactate accumulation and phosphocreatine utilization based on analysis of muscle biopsies obtained before and after each exercise. At the start of exercise, muscle temperature was 34.5°C (SD 1.7) in C compared with 37.2°C (SD 0.5) during HT ( P < 0.05). Thigh V̇o2after 3 min was 0.52 l/min (SD 0.11) in C and 0.63 l/min (SD 0.13) in HT, and at the end of exercise it was 0.60 l/min (SD 0.14) and 0.61 l/min (SD 0.10) in C and HT, respectively (not significant). Total lactate release was the same between the two temperature conditions, as was muscle lactate accumulation and PCr utilization. Total ATP production (aerobic + anaerobic) was the same between each temperature condition [505.0 mmol/kg (SD 107.2) vs. 527.1 mmol/kg (SD 117.6); C and HT, respectively]. In conclusion, within the range of temperatures studied, passively increasing muscle temperature before exercise has no effect on muscle energy turnover during dynamic exercise.
Tinnitus: Standard of Care, Personality Differences, Genetic Factors
Authors: Tyler Richard S. , Coelho Claudia , Noble William
Published: March 2006

We comment on three areas related to tinnitus. The standard of care should include counseling that is collaborative and that addresses the overall emotional well-being of the patient. Utilizing management and coping strategies is desirable. Our new tinnitus activities treatment is an example of such a protocol. We believe that the notions of fearfulness and acceptance have the potential to be integrated into tinnitus treatment. Some patients reject, control or accept their tinnitus. We believe in some instances there may be a common genetic cause of tinnitus and depression. A potential candidate is the serotonin transporter gene SLC6A4.
Tinnitus Retraining Therapy: A Different View on Tinnitus
Authors: Jastreboff Pawel J. , Jastreboff Margaret M.
Published: March 2006

Tinnitus retraining therapy (TRT) is a method for treating tinnitus and decreased sound tolerance, based on the neurophysiological model of tinnitus. This model postulates involvement of the limbic and autonomic nervous systems in all cases of clinically significant tinnitus and points out the importance of both conscious and subconscious connections, which are governed by principles of conditioned reflexes. The treatments for tinnitus and misophonia are based on the concept of extinction of these reflexes, labeled as habituation. TRT aims at inducing changes in the mechanisms responsible for transferring signal (i.e., tinnitus, or external sound in the case of misophonia) from the auditory system to the limbic and autonomic nervous systems, and through this, remove signal-induced reactions without attempting to directly attenuate the tinnitus source or tinnitus/misophonia-evoked reactions. As such, TRT is effective for any type of tinnitus regardless of its etiology. TRT consists of: (1) counseling based on the neurophysiological model of tinnitus, and (2) sound therapy (with or without instrumentation). The main role of counseling is to reclassify tinnitus into the category of neutral stimuli. The role of sound therapy is to decrease the strength of the tinnitus signal. It is crucial to assess and treat tinnitus, decreased sound tolerance, and hearing loss simultaneously. Results from various groups have shown that TRT can be an effective method of treatment.