bluuebunny/crossref_metadata_2025 huggingface dataset:
Model- and Information Theory-Based Diagnostic Method for Induction Motors
Authors: Lee Sanghoon , Bryant Michael D. , Karlapalem Lalit
Published: September 2006

Introduced is a model-based diagnostic system for motors, that also employs concepts of information theory as a health metric. From an existing bond graph of a squirrel cage induction motor, state equations were extracted and simulations performed. Simulated were various cases, including the response of an ideal motor, which functions perfectly to designer’s specifications, and motors with shorted stator coils, a bad phase capacitor, and broken rotor bars. By constructing an analogy between the motor and a communication channel, Shannon’s theorems of information theory were applied to assess functional health. The principal health metric is the channel capacity, which is based on integrals of signal-to-noise ratios. The channel capacity monotonically reduces with degradation of the system, and appears to be an effective discriminator of motor health and sickness. The method was tested via simulations of a three-phase motor; and for experimental verification, a two-phase induction motor was modeled and tested. The method was able to predict impending functional failure, significantly in advance.
Adaptive Nonlinear Synchronization Control of Twin-Gyro Precession
Authors: Zhou Di , Shen Tielong , Tamura Katsutoshi
Published: September 2006

The slewing motion of a truss arm driven by a V-gimbaled control-moment gyro is studied. The V-gimbaled control-moment gyro consists of a pair of gyros that must precess synchronously. For open-loop slewing motion control, the controller design problem is simplified into finding a feedback controller to steer the two gyros to synchronously track a specific command. To improve the synchronization performance, the integral of synchronization error is introduced into the design as an additional state variable. Based on the second method of Lyapunov, an adaptive nonlinear feedback controller is designed. For more accurate but complicated closed-loop slewing motion control, the feedback linearization technique is utilized to partially linearize the nonlinear nominal model, where two specific output functions are chosen to satisfy the system tracking and synchronization requirements. The system tracking dynamics are bounded by properly determining system indices and command signals. For the partially linearized system, the backstepping tuning function design approach is employed to design an adaptive nonlinear controller. The dynamic order of the adaptive controller is reduced to its minimum. The performance of the proposed controllers is verified by simulation.
Dynamic Constraint-Based Energy-Saving Control of Pneumatic Servo Systems
Authors: Al-Dakkan Khalid A. , Barth Eric J. , Goldfarb Michael
Published: September 2006

This paper proposes a control approach that can provide significant energy savings for the control of pneumatic servo systems. The control methodology is formulated by decoupling the standard four-way spool valve used for pneumatic servo control into two three-way valves, then using the resulting two control degrees of freedom to simultaneously satisfy a performance constraint (which for this paper is based on the sliding mode sliding condition), and an energy-saving dynamic constraint that minimizes cylinder pressures. The control formulation is presented, followed by experimental results that indicate significant energy savings with essentially no compromise in tracking performance relative to control with a standard four-way spool valve.
Nonlinear Model-Based Control of Pulse Width Modulated Pneumatic Servo Systems
Authors: Shen Xiangrong , Zhang Jianlong , Barth Eric J. , Goldfarb Michael
Published: September 2006

This paper presents a control methodology that enables nonlinear model-based control of pulse width modulated (PWM) pneumatic servo actuators. An averaging approach is developed to describe the equivalent continuous-time dynamics of a PWM controlled nonlinear system, which renders the system, originally discontinuous and possibly nonaffine in the input, into an equivalent system that is both continuous and affine in control input (i.e., transforms the system to nonlinear control canonical form). This approach is applied to a pneumatic actuator controlled by a pair of three-way solenoid actuated valves. The pneumatic actuation system is transformed into its averaged equivalent control canonical form, and a sliding mode controller is developed based on the resulting model. The controller is implemented on an experimental system, and the effectiveness of the proposed approach validated by experimental trajectory tracking.
Design for Feedback Systems With Plant Input Amplitude and Rate Saturation
Authors: Wu Wei , Jayasuriya Suhada
Published: September 2006

In this paper, a method of compensation for feedback systems subject to simultaneous plant input amplitude and rate saturation is presented. It applies to uncertain, stable plants of a type greater than or equal to 1. Founded on Horowitz’s original idea for amplitude saturation compensation (Horowitz, I., 1983, Int. J. Control, 38(1), pp. 169–197) and extensions developed in (Wu, W., and Jayasuriya, S., 1999, Proceedings of American Control Conference, San Diego, CA, pp. 3046–3050; Wu, W., and Jayasuriya, S., 2001, ASME J. Dyn. Syst., Meas., Control, 123(2), pp. 225–232; Wu, W., 2000, Ph.D. dissertation, Texas A&M University), a synthesis method that explicitly takes into account input amplitude and rate saturation is further developed. In the case of simultaneous amplitude and rate saturation, approaches developed separately for amplitude alone, and rate alone saturation (Wu, W., 2000, Ph.D. dissertation, Texas A&M University), respectively, are integrated into one method, and results in a 4DOF(degrees of freedom) feedback system with two extra compensators to deal with two saturation nonlinearities. Design constraints for saturation compensation are developed and expressed as frequency domain bounds. Synthesis of the two additional compensators follows from loop shaping methods, such as QFT. This approach guarantees input/output stability for the class of plants considered. Examples are given to illustrate the application of this approach.
Electromechanical Modeling of Piezoceramic Actuators for Dynamic Loading Applications
Authors: Georgiou Helen M. S. , Mrad Ridha Ben
Published: September 2006

In most piezoelectric applications, including precision motion control, pressure regulation in micropumps, and force control in microactuators, there is a need to develop a model that accounts for hysteresis and describes both the electrical and mechanical properties of piezoceramics, along with the electromechanical coupling between the two domains. A model that characterizes hysteresis and the coupled electromechanical effect of the sensing and actuating signals is presented. The model presented characterizes the electromechanical properties of a piezoceramic actuator when subject to variable mechanical load disturbance conditions. The model is tested under a range of voltage excitations at frequencies up to 111Hz and is shown to offer high accuracy.
Adaptive Controller and Observer Design for a Class of Nonlinear Systems
Authors: Zhu Yongliang , Pagilla Prabhakar R.
Published: September 2006

Design of a stable adaptive controller and observer for a class of nonlinear systems that contain product of unmeasurable states and unknown parameters is considered. The nonlinear system is cast into a suitable form based on which a stable adaptive controller and observer are designed using a parameter dependent Lyapunov function. The class of nonlinear systems considered is practically relevant; mechanical systems with dynamic friction fall into this category. Experimental results on a single-link mechanical system with dynamic friction are shown for the proposed design.
Performance Measures For Input Shaping and Command Generation
Authors: Kozak Kris , Singhose William , Ebert-Uphoff Imme
Published: September 2006

Many performance measures for input shaping and command generation have appeared in the literature, but very rarely have these measures been critically evaluated or thoroughly discussed. In this paper we review and discuss a number of key measures of residual vibration. These measures are clarified, and mathematical and graphical interpretations of these measures are developed. In addition, a set of energy-based vibration measures are presented for use in even the most general situations, such as measuring the vibration of a nonlinear, multimode system in response to an arbitrary command.
Characteristics of Fuel Droplets Discharged From a Compensated Fuel/Ballast Tank
Authors: Shan Jerry W. , Atsavapranee Paisan , Chang Peter A. , Wilson Wesley M. , Verosto Stephan
Published: September 2006

Fuel droplets, formed by the interaction of fuel plumes with a water/fuel interface, can be discharged during the refueling of water-filled compensated fuel/ballast tanks. Motivated by increasingly stringent environmental regulations, a study was initiated to understand the physical mechanisms involved in the formation and transport of fuel droplets by complex immiscible flows inside a model tank. In particular, optical measurements were made of the size distribution of fuel droplets in water discharged from a three-bay model of a compensated fuel/ballast tank. The volumetric fuel concentration of discharge from the tank was inferred from measurements of droplet size and number. Flow visualizations inside the model were coupled to optical measurements of fuel droplets at the tank outlet to show that the presence of fuel in the discharged water was correlated to the formation of fuel plumes within the water-filled tank. The size distribution of fuel droplets at the tank exit is found to differ from the size distribution reported for the generation zone (near the fuel plumes) inside the tank. Thus, the advection of fuel droplets from the generation zone to the tank outlet is shown to affect the characteristics of discharged fuel droplets. The transport process specifically prevents large-diameter droplets from reaching the tank exit. Buoyancy tends to cause larger fuel droplets generated within the tank to rise and separate out of the flow before they can be discharged. The buoyancy time, τb(D), relative to the characteristic advection time, τa, of fuel droplets is a key parameter in predicting the fate of fuel droplets. The influence of buoyancy on the size distribution of discharged droplets was found to be modeled reasonably well by a Butterworth filter that depends on the ratio of timescales τa∕τb(D). This model, which relates the size distribution of discharged droplets to generated droplets, is found to produce the correct qualitative behavior that larger fuel droplets are discharged when the fuel plumes move closer to the tank exit, i.e., for decreasing advection time τa.
Pressure Drop of Fully-Developed, Laminar Flow in Microchannels of Arbitrary Cross-Section
Authors: Bahrami M. , Yovanovich M. M. , Culham J. R.
Published: September 2006

The pressure drop of fully developed, laminar, incompressible flow in smooth mini- and microchannels of arbitrary cross-section is investigated. A compact approximate model is proposed that predicts the pressure drop for a wide variety of shapes. The model is only a function of geometrical parameters of the cross-section, i.e., area, perimeter, and polar moment of inertia. The proposed model is compared with analytical and numerical solutions for several shapes. Also, the comparison of the model with experimental data, collected by several researchers, shows good agreement.
Pressure-Driven Flows of Bingham Plastics Over a Square Cavity
Authors: Mitsoulis Evan , Marangoudakis S. , Spyratos M. , Zisis Th. , Malamataris Nikolaos A.
Published: September 2006

Pressure-driven flows over a square cavity are studied numerically for Bingham plastics exhibiting a yield stress. The problem is encountered whenever pressure measurements are made by a drilled-hole based pressure transducer. The Bingham constitutive equation is used with an appropriate modification proposed by Papanastasiou, which applies everywhere in the flow field in both yielded and practically unyielded regions. Newtonian results are obtained for a wide range of Reynolds numbers (0<Re≤1000) for the cavity vortex position and intensity, and the excess pressure drop (entrance correction) in the system. To reduce the length of the computational domain for highly convective flows, an open boundary condition has been implemented at the outflow. For viscoplastic fluids the emphasis is on determining the extent and shape of yielded/unyielded regions along with the cavity vortex shape, size, and intensity for a wide range of Bingham numbers (0≤Bn<∞). The entrance correction is found to be an increasing sigmoidal function of the Bn number, reaching asymptotically the value of zero. It is shown that for viscoplastic fluids not exhibiting normal stresses in shear flow (lack of viscoelasticity), the hole pressure is zero opposite the center of the hole. Thus, any nonzero pressure hole measured by this apparatus would signify the presence of a normal-stress difference in the fluid.
Air Flow Through Compressed and Uncompressed Aluminum Foam: Measurements and Correlations
Authors: Dukhan Nihad , Picón-Feliciano Rubén , Álvarez-Hernández Ángel R.
Published: September 2006

Wind-tunnel steady-state unidirectional pressure-drop measurements for airflow through nine compressed and uncompressed isotropic open-cell aluminum foam samples, having different porosities and pore densities, were undertaken. The compressed foam produced significantly higher pressure drop, which increased with increasing Darcian velocity following the quadratic Forchheimer equation. The permeability and the inertia coefficient data for the compressed foam showed less scatter compared to those for the uncompressed foam. Both were correlated using an Ergun-like equation, with the correlation being better for the permeability. The permeability correlation predicted the results of some previous studies very well. The friction factor correlated well with the Reynolds number.
RANS Simulations of a Simplified Tractor/Trailer Geometry
Authors: Roy Christopher J. , Payne Jeffrey , McWherter-Payne Mary
Published: September 2006

Steady-state Reynolds-averaged Navier-Stokes (RANS) simulations are presented for the three-dimensional flow over a simplified tractor/trailer geometry at zero degrees yaw angle. The simulations are conducted using a multi-block, structured computational fluid dynamics (CFD) code. The turbulence closure model employed is the two-equation Menter k-ω model. The discretization error is estimated by employing two grid levels: a fine mesh of 20 million cells and a coarser mesh of 2.5 million cells. Simulation results are compared to experimental data obtained at the NASA-Ames 7×10ft wind tunnel. Quantities compared include vehicle drag, surface pressures, and time-averaged velocities in the trailer near wake. The results indicate that the RANS approach is able to accurately predict the surface pressure on the vehicle, with the exception of the base region. The pressure predictions in the base region are poor due to the inability of the RANS model to accurately capture the near-wake vortical structure. However, the gross pressure levels in the base region are in reasonable agreement with experiment, and thus the overall vehicle drag is well predicted.
State-space Model Identification Using Input and Output Data With Steady State Values Zeroing Multiple Integrals of Output Error
Authors: Kosaka Manabu , Uda Hiroshi , Bamba Eiichi , Shibata Hiroshi
Published: September 2006

This study proposes a new deterministic off-line identification method that obtains a state-space model using input and output data with steady state values. This method comprises of two methods: Zeroing the 0∼N-tuple integral values of the output error of single-input single-output transfer function model (Kosaka et al., 2004) and Ho-Kalman’s method (Zeiger and McEwen, 1974). Herein, we present a new method to derive a matrix similar to the Hankel matrix using multi-input and multi-output data with steady state values. State space matrices A, B, C, and D are derived from the matrix by the method shown in Zeiger and McEwen, 1974 and Longman and Juang, 1989. This method’s utility is that the derived state-space model is emphasized in the low frequency range under certain conditions. Its salient feature is that this method can identify use of step responses; consequently, it is suitable for linear mechanical system identification in which noise and vibration are unacceptable. Numerical simulations of multi-input multi-output system identification are illustrated.
Parametric Identification for Second-Order Nonlinear Systems in Closed-Loop Operations
Authors: Huang Jeng-Tze
Published: September 2006

A new scheme for identifying the parameters of second-order nonlinear systems, including those affine with the control input, is presented. First, a high-gain PD control is applied for the tracking of a prescribed reference trajectory, along which the regressor is persistently excited. Next, a parameter observer, modified from Huang (Huang, J. T., 2002, “An Adaptive Compensator for a Class of Linearly Parameterized Systems,” IEEE Trans. Automat. Control, 47(3), pp. 483–486), is constructed to achieve the desired goals. Comparing to conventional methodologies, it is easier to implement for no acceleration signals or filtering of the system states being involved. Numerical examples are given in the final to demonstrate its effectiveness.
Robust H∞ Control and Stabilization of Uncertain Switched Linear Systems: A Multiple Lyapunov Functions Approach
Authors: Ji Zhijian , Guo Xiaoxia , Wang Long , Xie Guangming
Published: September 2006

This paper addresses robust H∞ control and stabilization of switched linear systems with norm-bounded time-varying uncertainties. First, based on multiple Lyapunov functions methodology, a sufficient condition is derived for robust stabilization with a prescribed disturbance attenuation level γ only by employing state-dependent switching rules. Then the robust H∞ control synthesis via switched state feedback is studied. It is shown that a switched state-feedback controller can be designed to stabilize the switched systems with an H∞-norm bound if a matrix inequality based condition is feasible. This condition can be dealt with as linear matrix inequalities (LMIs) provided that the associated parameters are selected in advance. All the results presented can be regarded as an extension of some existing results for both switched and nonswitched systems.
Boundary Layer Eigenvalues in SISO Discrete-Time Sliding Mode Control with Observer
Authors: Richter Hanz , Misawa Eduardo A.
Published: September 2006

A result that allows us to specify the sliding manifold in observer-based discrete-time sliding mode control is presented. Selection of coefficients is done by analyzing the tracking error dynamics inside the boundary layer, where the closed-loop system has a linear state feedback configuration, rather than assuming that ideal sliding occurs. The result facilitates assignment of eigenvalues for the system matrix which defines such linear dynamics.
The Classical Plane Couette-Poiseuille Flow With Variable Fluid Properties
Authors: Pantokratoras Asterios
Published: September 2006

A theoretical study of the effect of variable viscosity and variable thermal conductivity on the classical plane Couette-Poiseuille flow is presented in this brief communication. The investigation concerns engine oil, air, and water taking into account the variation of these quantities with temperature. The results are obtained with the numerical simulation of the governing equations and cover large temperature differences. Velocity and temperature profiles are presented as well as the volume flow rate and the heat flux between the plates. It is found that temperature profiles are close to the straight line for oil and water and depart significantly from the straight line for air due to nonlinear thermal conductivity. Dynamic viscosity plays an important role on the results which depart significantly from those of a fluid with constant properties.
Moderately and Widely Spaced Circular Cylinders in Crossflow and a Universal Wake Number
Authors: Sumner D. , Schenstead A. J.
Published: September 2006

The universal wake number concept was examined for the flow around two circular cylinders of equal diameter arranged in moderately and widely spaced staggered configurations. The experiments were conducted in the subcritical Reynolds number regime for P∕D=1.5–4.0. The results establish new limits for the validity of the universal wake number concept for moderately and widely spaced staggered cylinders in crossflow, and extend the results of an earlier study that focused only on closely spaced staggered cylinders.
Numerical Simulation of Two-Dimensional Laminar Incompressible Wall Jet Flow Under Backward-Facing Step
Authors: Kanna P. Rajesh , Das Manab Kumar
Published: September 2006

Two-dimensional laminar incompressible wall jet flow over a backward-facing step is solved numerically to gain insight into the expansion and recirculation of flow processes. Transient streamfunction vorticity formulation of the Navier-Stokes equation is solved with clustered grids on the physical domain. The behavior of the jet has been studied for different step geometry (step length, l, step height, s) and Reynolds number (Re). It is found that the presence of a step in the wall jet flow creates recirculation and the reattachment length follows an almost linear trend within the range considered for both parameters Re and step geometry. Simulations are made to show the effect of entrainment on recirculation eddy. Detailed study of u velocity decay is reported. The velocity profile in the wall jet region shows good agreement with experimental as well as similarity results. The distance where the similarity profile forms is reduced by increasing the step geometry whereas an increment in Re increases this distance. The effects of Re, step length, and step height on wall vorticity are presented. The parametric study is helpful to predict the reattachment location for wall jet flows over step.
Numerical Study of Unsteady Flows in a Scroll Compressor
Authors: Cui M. M.
Published: September 2006

Since scroll compressors contain gas pockets whose shapes and sizes change continuously, the flow fields inside the compressors are time dependent and three-dimensional. The spatial and temporal variations inside the gas pockets also induce unsteady flows between the gas pockets. This unsteadiness controls the mechanisms responsible for the behavior of the scroll compressor components and their interactions. The dynamic nature inherent in the scroll compressors affects the performance and reliability of the scroll compressors. To improve and optimize the scroll compressor design for better performance and reliability, information is needed to understand the detailed physics of the unsteady flows inside the scroll compressors. To provide the fundamental information needed, the unsteady flows in a scroll compressor are studied numerically. The system simulated includes upper bearing housing, scrolls, check valve, and discharge plenum. Refrigerant-22 is used as the working fluid. The unsteady flows inside and between the gas pockets are characterized by the instantaneous distributions of field quantities and the area- and mass-averaged parameters.
SINGLE AND MULTIPLE VALUED LOCALIZED EXCITATIONS OF BOITI-LEON-PEMPINELLI SYSTEM IN (2+1)-DIMENSIONS VIA A MAPPING METHOD
Authors: ZHENG CHUN-LONG , ZHU HAI-PING , XIE LIN-SEN , FANG JIAN-PING
Published: September 2006

With the help of a mapping approach, a new type of variable separation solution with two arbitrary functions to (2+1)-dimensional Boiti–Leon–Pempinelli system (BLP) is derived. Based on the derived variable separation solution, some single valued and multiple valued localized excitations such as dromions, peakons and foldons, etc. with novel evolutional properties are revealed by introducing appropriate initial conditions in this paper.
Aldo-Keto Reductases and Bioactivation/Detoxication
Authors: Jin Yi , Penning Trevor M.
Published: September 2006

Aldo-keto reductases (AKRs) are soluble NAD(P)(H) oxidoreductases that primarily reduce aldehydes and ketones to primary and secondary alcohols, respectively. The ten known human AKR enzymes can turnover a vast range of substrates, including drugs, carcinogens, and reactive aldehydes. They play central roles in the metabolism of these agents, and this can lead to either their bioactivation or detoxication. AKRs are Phase I drug metabolizing enzymes for a variety of carbonyl-containing drugs and are implicated in cancer chemotherapeutic drug resistance. They are involved in tobacco-carcinogenesis because they activate polycyclic aromatic trans-dihydrodiols to yield reactive and redox active o-quinones, but they also catalyze the detoxication of nicotine derived nitrosamino ketones. They also detoxify reactive aldehydes formed from exogenous toxicants, e.g., aflatoxin, endogenous toxicants, and those formed from the breakdown of lipid peroxides. AKRs are stress-regulated genes and play a central role in the cellular response to osmotic, electrophilic, and oxidative stress.
Stop That Cell! β-Arrestin-Dependent Chemotaxis: A Tale of Localized Actin Assembly and Receptor Desensitization
Authors: DeFea Kathryn A.
Published: September 2006

β-arrestins have recently emerged as key regulators of directed cell migration or chemotaxis. Given their traditional role as mediators of receptor desensitization, one theory is that β-arrestins contribute to cell polarity during chemotaxis by quenching the signal at the trailing edge of the cell. A second theory is that they scaffold signaling molecules involved in cytoskeletal reorganization to promote localized actin assembly events leading to the formation of a leading edge. This review addresses both models. It discusses studies demonstrating the involvement of β-arrestins in chemotaxis both in vivo and in vitro as well as recent evidence that β-arrestins directly bind and regulate proteins involved in actin reorganization.
Effects of pioglitazone and metformin on β-cell function in nondiabetic subjects at high risk for type 2 diabetes
Authors: Rasouli Neda , Kern Philip A , Reece E. Albert , Elbein Steven C.
Published: September 2006

Thiazolidinediones (TZDs) and metformin decreased the incidence of diabetes in subjects at risk for developing diabetes and improved peripheral or hepatic insulin sensitivity, respectively. Whether they also directly improved β-cell function is not clear. In vitro studies showed improved β-cell function in response to TZDs and metformin; however, the effects of TZDs or metformin on β-cell function in humans are still uncertain. We hypothesized that both TZDs and metformin directly affect β-cell function. We evaluated β-cell function and insulin sensitivity (SI) in subjects with impaired glucose tolerance or a history of gestational diabetes using oral and intravenous glucose tolerance tests in addition to the glucose-potentiated arginine stimulation test. In contrast to metformin, pioglitazone improved SI, glucose tolerance, and insulin-independent glucose disposal [glucose effectiveness (SG)]. Neither pioglitazone nor metformin significantly improved β-cell compensation for insulin resistance [disposition index (DI)], but the change in DI significantly correlated with baseline SI. Insulin secretion in response to arginine at maximally potentiating glucose levels (AIRmax) tended to increase after metformin and to decrease after pioglitazone; however, when adjusted for SI, the changes were not significant. Our results demonstrate that, in nondiabetic subjects at risk for diabetes, pioglitazone, but not metformin, significantly improved glucose tolerance by improving SI and SG. We did not find any evidence that either pioglitazone or metformin improved β-cell function. Improved β-cell compensation was observed primarily in the subgroup of subjects that had the lowest SI at baseline.
Spontaneously reduced blood pressure load in the rat streptozotocin-induced diabetes model: potential pathogenetic relevance
Authors: Bidani Anil K. , Picken Maria , Hacioglu Rifat , Williamson Geoffrey , Griffin Karen A.
Published: September 2006

The rat streptozotocin (STZ)-induced diabetes model is widely used to investigate the pathogenesis of diabetic nephropathy. However, overt nephropathy is inexplicably slow to develop in this model compared with renal mass reduction (RMR) models. To examine whether blood pressure (BP) differences correlated with the time course of glomerulosclerosis (GS), BP was measured continuously throughout the course by radiotelemetry in control ( n = 17), partially insulin-treated STZ-diabetes (average blood glucose 364 ± 15 mg/dl; n = 15), and two normotensive RMR models (systolic BP <140 mmHg)—uninephrectomy (UNX; n = 16) and 3/4 RMR by surgical excision [right nephrectomy + excision of both poles of left kidney (RK-NX); n = 12] in Sprague-Dawley rats. Proteinuria and GS were assessed at ∼16–20 wk (all groups) and at 36–40 wk (all groups except RK-NX). At 16 wk, significantly greater proteinuria and GS had developed in the RK-NX group compared with the other three groups (not different from each other). By 36–40 wk, substantial proteinuria and GS had also developed in the UNX group, but both the control and the STZ-diabetic rats exhibited comparable modest proteinuria and minimal GS. Systolic BP (mmHg) was significantly reduced in the STZ-diabetic rats (116 ± 1.1) compared with both control (124 ± 1.0) and RMR (128 ± 1.2 and 130 ± 3.0) groups ( P < 0.01). Similarly, “BP load” as estimated by BP power spectral analysis was also lower in the STZ-diabetic rats. Given the known protective effects of BP reductions on the progression of diabetic nephropathy, it is likely that this spontaneous reduction in ambient BP contributes to the slow development of GS in the STZ-diabetes model compared with the normotensive RMR models.
Evidence that calcineurin is required for the genesis of bone-resorbing osteoclasts
Authors: Sun Li , Peng Yuanzhen , Zaidi Neeha , Zhu Ling-Ling , Iqbal Jameel , Yamoah Kosj , Wang Xin , Liu Peng , Abe Etsuko , Moonga Baljit S. , Epstein Solomon , Zaidi Mone
Published: September 2006

Here, we demonstrate that the Ca2+/calmodulin-sensitive phosphatase calcineurin is a necessary downstream mediator for osteoclast differentiation. Using quantitative PCR, we detected the calcineurin isoforms Aα, Aβ, Aγ (catalytic), and B1 (regulatory) in osteoclast precursor RAW-C3 cells. We found that, although the expression of these isoforms remained relatively unchanged during osteoclast differentiation, there was a profound increase in the expression of their primary substrate for calcineurin, nuclear factor of activated T cells (NFAT)c1. For gain-of-function studies, we incubated osteoclast precursors for 10 min with a calcineurin fusion protein (TAT-calcineurin Aα); this resulted in its receptorless influx into >90% of the precursor cells. A marked increase in the expression of the osteoclast differentiation markers tartrate-resistant acid phosphatase (TRAP) and integrin β3 followed. In addition, the expression of NFATc1, as well as the alternative substrate for calcineurin, IκBα, was significantly enhanced. Likewise, transfection with constitutively active NFAT resulted in an increased expression of both TRAP and integrin β3. In parallel loss-of-function studies, transfection with dominant-negative NFAT not only inhibited osteoclast formation but also reversed the induction of NFATc1, TRAP, and integrin β3 by TAT-calcineurin Aα. The expression of these markers was also inhibited by calcineurin Aα U1 small nuclear RNA, which significantly reduced calcineurin Aα mRNA and protein expression. Consistent with these observations, we observed a reduction in osteoclastogenesis in calcineurin Aα−/− cells and in osteoclast precursors treated with the calcineurin inhibitors cyclosporin A and FK506. Together, the gain- and loss-of-function experiments establish that calcineurin Aα is necessary for osteoclast formation from its precursor and that this occurs via an NFATc1-dependent mechanism.
Residual Bound Ca2+ Can Account for the Effects of Ca2+ Buffers on Synaptic Facilitation
Authors: Matveev Victor , Bertram Richard , Sherman Arthur
Published: September 2006

Facilitation is a transient stimulation-induced increase in synaptic response, a ubiquitous form of short-term synaptic plasticity that can regulate synaptic transmission on fast time scales. In their pioneering work, Katz and Miledi and Rahamimoff demonstrated the dependence of facilitation on presynaptic Ca2+ influx and proposed that facilitation results from the accumulation of residual Ca2+ bound to vesicle release triggers. However, this bound Ca2+ hypothesis appears to contradict the evidence that facilitation is reduced by exogenous Ca2+ buffers. This conclusion led to a widely held view that facilitation must depend solely on the accumulation of Ca2+ in free form. Here we consider a more realistic implementation of the bound Ca2+ mechanism, taking into account spatial diffusion of Ca2+, and show that a model with slow Ca2+ unbinding steps can retain sensitivity to free residual Ca2+. We demonstrate that this model agrees with the facilitation accumulation time course and its biphasic decay exhibited by the crayfish inhibitor neuromuscular junction (NMJ) and relies on fewer assumptions than the most recent variants of the free residual Ca2+ hypothesis. Further, we show that the bound Ca2+ accumulation is consistent with Kamiya and Zucker's experimental results, which revealed that photolytic liberation of a fast Ca2+ buffer decreases the synaptic response within milliseconds. We conclude that Ca2+ binding processes with slow unbinding times (tens to hundreds of milliseconds) constitute a viable mechanism of synaptic facilitation at some synapses and discuss the experimental evidence for such a mechanism.
Multisensory Orientation Behavior Is Disrupted by Neonatal Cortical Ablation
Authors: Jiang Wan , Jiang Huai , Rowland Benjamin A. , Stein Barry E.
Published: September 2006

The integration of visual and auditory information can significantly amplify the sensory responses of superior colliculus (SC) neurons and the behaviors that depend on them. This response amplification depends on the development of SC inputs that are derived from two regions of cortex: the anterior ectosylvian sulcus (AES) and the rostral lateral suprasylvian sulcus (rLS). Neonatal ablation of these cortico-collicular areas has been shown to disrupt the development of the multisensory enhancement capabilities of SC neurons and the present results demonstrate that it also precludes the development of the normal multisensory enhancements in orientation behavior. Animals with neonatal ablation of AES and rLS were tested at maturity and found unable to benefit from the combination of visual and auditory cues in their efforts to localize targets in contralesional space. In contrast, their ipsilesional multisensory orientation capabilities were indistinguishable from those of normal animals. However, when only one of these cortical areas was removed during early life, later behavioral consequences were negligible. Whether similar compensatory processes would occur in adult animals remains to be determined. These observations, coupled with those from previous studies, also suggest that a surprisingly high proportion of SC neurons capable of multisensory integration must be present for orientation behavior benefits to be realized. Compensatory mechanisms can achieve this if early lesions spare either AES or rLS, but even the impressive plasticity of the neonatal brain cannot compensate for the early loss of both of them.
Hypothesis of quantum as a distributed self‐organized computation by collective of particles
Authors: Kurakin Pavel V.
Published: September 2006

Previously we suggested an
original interpretation of quantum mechanics. The interpretation
supposes that quantum probability amplitudes are a manifestation
of self‐organization of nature at some deeper level of matter,
performed in spatially and temporally distributed manner. Instead
of formal description of the concept, the paper shows in detail
how it works for basic quantum experiments.
Extinction and permanence of two‐nutrient and one‐microorganism chemostat model with pulsed input
Authors: Song Xinyu , Zhao Zhong
Published: September 2006

A chemostat model with periodically pulsed input is considered. By
using the Floquet theorem, we find that the microorganism eradication
periodic solution is globally asymptotically stable if the impulsive period T is more than a critical value. At the same time we can find that the nutrient and
microorganism are permanent if the impulsive period T is less than the critical value.
Dynamics of a nonautonomous semiratio‐dependent predator‐prey system with nonmonotonic functional responses
Authors: Huo Hai-Feng , Li Wan-Tong
Published: September 2006

A nonautonomous semiratio‐dependent predator‐prey system with
nonmonotonic functional responses is investigated. For general
nonautonomous case, positive invariance, permanence, and globally
asymptotic stability for the system are studied. For the periodic
(almost periodic) case, sufficient conditions for existence,
uniqueness, and stability of a positive periodic (almost periodic)
solution are obtained.
Stability and assignment of spectrum in systems with discrete time lags
Authors: De la Sen M.
Published: September 2006

The asymptotic stability with a prescribed degree of time delayed
systems subject to multiple bounded discrete delays has received
important attention in the last years. It is basically proved that the α‐stability locally in the delays (i.e., all the eigenvalues have
prefixed strictly negative real parts located in Re⁡s ≤ −α < 0) may be tested for a set of admissible delays
including possible zero delays either through a set of Lyapunov′s
matrix inequalities or, equivalently, by checking that an
identical number of matrices related to the delayed dynamics
are all stability matrices. The result may be easily
extended to check the ε‐asymptotic stability independent of the delays, that is, for all the delays having any
values, the eigenvalues are stable and located in Re⁡s ≤ ε → 0−. The above referred number of stable matrices to be tested is 2r for a set of distinct r point delays and includes all possible
cases of alternate signs for summations for all the matrices of
delayed dynamics. The manuscript is
completed with a study for prescribed closed‐loop spectrum
assignment (or “pole placement”) under output feedback.
Detection of the permutation symmetry in pattern sets
Authors: Ji-Yang Dong , Jun-Ying Zhang
Published: September 2006

Symmetry is a powerful tool to reduce the freedom degrees of a system. But the applicability of the symmetry tool strongly depends on the ability to calculate the symmetries of the system. There exists an interesting algorithmic problem to search for the symmetry of a high‐dimensional system. In this paper, a genetic algorithm‐based permutation symmetry detection approach is proposed for pattern set. Firstly, the permutation symmetry distance (PSD) is defined to measure the similarity of a pattern set before and after being transformed by a permutation operator. Secondly, the permutation symmetry detection problem is converted into an optimization problem by taking the PSD as a fitness function. Lastly, a genetic algorithm‐based approach is designed for the symmetry detection problem. Computer simulation results are also given for five pattern sets of different dimensionality, which show the efficiency and speediness of the proposed detection approach, especially in high‐dimensional cases.
Exponential stability of a kind of stochastic delay difference equations
Authors: Ding Xiaohua
Published: September 2006

We present a Razumilchin‐type theorem for stochastic delay
difference equation, and use it to investigate the mean square
exponential stability of a kind of nonautonomous stochastic
difference equation which may also be viewed as an approximation
of a nonautonomous stochastic delay integrodifferential
equations (SDIDEs), and of a difference equation arises from some
of the earliest mathematical models of the macroeconomic “trade
cycle” with the environmental noise.
Severe Life Threatening Maxillofacial Infection in Pregnancy Presented as Ludwig′s Angina
Authors: Abramowicz Shelly , Abramowicz Jacques S. , Dolwick M. Franklin
Published: September 2006

Background. Ludwig′s angina is a rapidly spreading
cellulitis that may produce upper airway obstruction often leading
to death. There is very little published information regarding
this condition in the pregnant patient. Case. A 24‐year
old black female was admitted at 26 weeks gestation with tooth
pain, submandibular swelling, severe trismus, and dysphagea,
consistent with Ludwig′s angina. Her treatment included emergent
tracheostomy, incision and drainage of associated spaces, teeth
extraction, and antibiotic therapy. Conclusions. During a
life threatening infectious situation such as the one described,
risks of maternal and fetal morbidity include both septicemia and
asphyxia. Furthermore, the healthcare provider must consider the
risks that the condition and the possible treatments may cause the
mother and her unborn child.
A Hybrid Approach of Using Wavelets and Fuzzy Clustering for Classifying Multispectral Florescence In Situ Hybridization Images
Authors: Wang Yu-Ping , Dandpat Ashok Kumar
Published: September 2006

Multicolor or multiplex fluorescence in situ hybridization (M‐FISH) imaging is a recently developed molecular cytogenetic diagnosis technique for rapid visualization of genomic aberrations at the chromosomal level. By the simultaneous use of all 24 human chromosome painting probes, M‐FISH imaging facilitates precise identification of complex chromosomal rearrangements that are responsible for cancers and genetic diseases. The current approaches, however, cannot have the precision sufficient for clinical use. The reliability of the technique depends primarily on the accurate pixel‐wise classification, that is, assigning each pixel into one of the 24 classes of chromosomes based on its six‐channel spectral representations. In the paper we introduce a novel approach to improve the accuracy of pixel‐wise classification. The approach is based on the combination of fuzzy clustering and wavelet normalization. Two wavelet‐based algorithms are used to reduce redundancies and to correct misalignments between multichannel FISH images. In comparison with conventional algorithms, the wavelet‐based approaches offer more advantages such as the adaptive feature selection and accurate image registration. The algorithms have been tested on images from normal cells, showing the improvement in classification accuracy. The increased accuracy of pixel‐wise classification will improve the reliability of the M‐FISH imaging technique in identifying subtle and cryptic chromosomal abnormalities for cancer diagnosis and genetic disorder research.
Automated Analysis of Fluorescence Microscopy Images to Identify Protein‐Protein Interactions
Authors: Venkatraman S. , Doktycz M. J. , Qi H. , Morrell-Falvey J. L.
Published: September 2006

The identification of protein interactions is important for elucidating biological networks. One obstacle in comprehensive interaction studies is the analyses of large datasets, particularly those containing images. Development of an automated system to analyze an image‐based protein interaction dataset is needed. Such an analysis system is described here, to automatically extract features from fluorescence microscopy images obtained from a bacterial protein interaction assay. These features are used to relay quantitative values that aid in the automated scoring of positive interactions. Experimental observations indicate that identifying at least 50% positive cells in an image is sufficient to detect a protein interaction. Based on this criterion, the automated system presents 100% accuracy in detecting positive interactions for a dataset of 16 images. Algorithms were implemented using MATLAB and the software developed is available on request from the authors.
FDK Half‐Scan with a Heuristic Weighting Scheme on a Flat Panel Detector‐Based Cone Beam CT (FDKHSCW)
Authors: Yang Dong , Ning Ruola
Published: September 2006

A cone beam circular half‐scan scheme is becoming an attractive imaging method in cone beam CT since it improves the temporal resolution. Traditionally, the redundant data in the circular half‐scan range is weighted by a central scanning plane‐dependent weighting function; FDK algorithm is then applied on the weighted projection data for reconstruction. However, this scheme still suffers the attenuation coefficient drop inherited with FDK when the cone angle becomes large. A new heuristic cone beam geometry‐dependent weighting scheme is proposed based on the idea that there exists less redundancy for the projection data away from the central scanning plane. The performance of FDKHSCW scheme is evaluated by comparing it to the FDK full‐scan (FDKFS) scheme and the traditional FDK half‐scan scheme with Parker′s fan beam weighting function (FDKHSFW). Computer simulation is employed and conducted on a 3D Shepp‐Logan phantom. The result illustrates a correction of FDKHSCW to the attenuation coefficient drop in the off‐scanning plane associated with FDKFS and FDKHSFW while maintaining the same spatial resolution.
Total Variation Wavelet‐Based Medical Image Denoising
Authors: Wang Yang , Zhou Haomin
Published: September 2006

We propose a denoising algorithm for medical images based on a combination of the total variation minimization scheme and the wavelet scheme. We show that our scheme offers effective noise removal in real noisy medical images while maintaining sharpness of objects. More importantly, this scheme allows us to implement an effective automatic stopping time criterion.
Virtual Contrast for Coronary Vessels Based on Level Set Generated Subvoxel Accurate Centerlines
Authors: Bitter Ingmar , Van Uitert Robert , Wolf Ivo , Tzatha Efstathia , Gharib Ahmed M , Summers Ronald , Meinzer Hans-Peter , Pettigrew Roderic
Published: September 2006

We present a tool for tracking coronary vessels in MRI scans of the human heart to aid in the screening of heart diseases. The vessels are identified through a single click inside each vessel present in a standard orthogonal view. The vessel identification results from a series of computational steps including eigenvalue analysis of the Hessian of the MRI image followed by a level set‐based extraction of the vessel centerline. All identified vessels are highlighted using a virtual contrast agent and displayed simultaneously in a spherical curved reformation view. In cases of over segmentation, the vessel traces can be shortened by a click on each vessel end point. Intermediate analysis results of the vessel computation steps can be displayed as well. We successfully validated the tool on 40 MRI scans demonstrating accuracy and significant time savings over manual vessel tracing.