bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct solution to an optimal control problem of econometric systems
Authors: Kabe D. G. , Rao U. L. Gouranga
Published: July 2007

A direct solution is proposed to an optimal control problem of linear econometric systems with a quadratic welfare loss function when there are linear equality constraints on the control variables. The direct solution proposed here eliminates the problem of non‐uniqueness of the optimal solution, which is present when this optimal control problem is solved using the recursive algorithm proposed by Chow,1 Pindyck2 and Tan.3 If a unique solution to the optimal control problem exists, then the direct solution and the recursive solution coincide.
Exact penalty function approach to constrained optimal control problems
Authors: Xing A. Q. , Chen Z. H. , Wang C. L. , Yao Y. Y.
Published: July 2007

Given the well known concept that optimal control problems may be solved either by the maximum principle or by the dynamic programming technique which employs many numerical algorithms, this paper attempts to show that the exact penalty function method may be used to transform a constrained optimal control problem into an unconstrained optimal control problem. Under certain conditions the constrained optimal control problem is shown to be equivalent to an unconstrained optimal control problem, which can be easily solved by a numerical technique.
A real‐time solution for preventive and repair maintenance
Authors: Gaimon Cheryl , Thompson Gerald L.
Published: July 2007

A deterministic approach to a single‐machine maintenance problem is presented which is solved forward in real‐time. The importance of real‐time solutions is particularly evident in new manufacturing environments, where fast decisions reflecting the most current information are vital to obtain high utilization of expensive equipment and to avoid bottlenecks in the production process. A sequential decision‐making process in introduced. First, the model presented is solved at the initial time when the machine is purchased. Then, each time a breakdown occurs, the model is solved again using the updated breakdown information. The initial solution contains the optimal preventive maintenance policy and the optimal resale time of the machine assuming it remains functional. At each breakdown time, the optimal breakdown‐repair policy is obtained indicating whether a repair should be made or whether the broken machine should be junked. If a repair is made, then the optimal preventive maintenance policy and resale time of the machine are derived. It is shown that if a breakdown occurs following the interval in which preventive maintenance is optimally applied, then a repair is not advocated and the machine is junked. In addition, a method for deriving the future expected times of machine failures is presented. Therefore, in addition to the optimal decisions corresponding to the realized behaviour to the machine, optimal policies are derived which consider its future expected performance.
Optimal advertising and pricing for a three‐stage time‐lagged monopolistic diffusion model incorporating income
Authors: Jedidi Kamel , Eliashberg Jehoshua , Desarbo Wayne S.
Published: July 2007

A three‐stage time‐lagged diffusion model that incorporates consumers' income, advertising and price effects is proposed. The derivation of the model synthesizes and relies upon a number of important arguments made in the diffusion and economic literature. Optimal control theory is used to derive normative advertising and pricing strategic implications for a monopolist introducing a new durable product.
R & D Spending and product pricing
Authors: Erickson Gary M.
Published: July 2007

An optimal control model is developed that combines cost reduction through R & D with pricing. Price and R & D spending level are control variables and unit cost is a state variable. Analysis of the model reveals that if a firm has a positive discount rate, optimal R & D spending on cost reduction may grow to a peak before eventually declining. If the firm has a zero discount rate, optimal R & D spending declines monotonically across time. Optimal price declines monotonically in either case, in a direct relationship with unit cost.
Mixed h2 and h∞ optimal robust control design
Authors: Sparks Andrew G. , Yeh Hsi‐Han , Banda Siva S.
Published: July 2007

This paper introduces a design methodology for a dynamic compensator that simultaneously minimizes the upper bound of a quadratic performance index and the H∞‐norm of a disturbance transfer function matrix of a multiple‐input/multiple‐output system whose model contains parameter uncertainty in the state and input matrices. The real parameter uncertainty is modelled as additional measurement outputs and as additional weights on the existing noise inputs and measurement outputs of the system. The compensator equations are derived by taking the dual of a system with parameter variation in the state and output matrices, for which the compensator equations have previously been derived, and then taking the dual of the compensator equations. An algorithm for applying this theory is given and an example is shown.
Robust quadratic optimization of systems with large parameter variations
Authors: Eslami Mansour
Published: July 2007

In this paper, two new algorithms to synthesize robust controllers which tolerate large parameter variations in the system are presented. The new analytical procedure that has led to the establishment of these algorithms can be easily used to solve similar perturbational problems when small‐sensitivity measures are used. These algorithms are applied to a numerical example to show the system performance under these design methodologies and to compare the final outcomes of these algorithms.
Optimal temperature control of jacket‐cooled fermentation reactors
Authors: Gee Douglas A. , Ramirez W. Fred
Published: July 2007

For systems such as jacketed vessels with significant dead time, cooling jacket dynamics and unpredictable but measurable load disturbances, advanced control concepts need to be used in order to achieve quality regulatory control. In the current work, optimal regulatory control theory has been applied to this problem. An optimal control algorithm is used to effectively control a batch fermentation reactor. The algorithm is easily implementable and very effective. It is capable of responding to both measurable and unmeasurable process disturbances.
Stability and identifiability of parameters in Galerkin approximation of distributed systems under multiple inputs
Authors: Kunisch K. , White L.
Published: July 2007

In this communication we consider conditions for stability and identifiability of parameters in initial value problems governed by systems of ordinary differential equations that are obtained as Galerkin approximations of parabolic initial boundary value problems. Of particular interest are problems in which multiple inputs are allowed to obtain multiple outputs. These input—output relations are used to obtain the desired identifiability results.
Multipurpose controller design in multivariable stochastic control systems
Authors: Baṅka S.
Published: July 2007

The paper presents a computer‐aided procedure for multipurpose controller design which in multivariable (linearized) stochastic systems simultaneously ensures (1) complete dynamic decoupling of control loops, (2) arbitrary closed‐loop pole placement and internal stability of the control system, (3) steady state output rejection of non‐zero mean values of disturbances as well as zero steady state regulation and/or tracking errors, (4) reduction of amplitude modulation of the control signals and (5) optimal steady state estimation of the plant's state and output vectors. The polynomial matrix approach in the frequency s‐domain is used to solve the stochastic control problem. Numerical results and simulations for a simplified version of a ship‐positioning control system design are presented to illustrate characteristics of the problem.
A modified optimal load‐frequency controller for interconnected power systems
Authors: Liaw C. M.
Published: July 2007

This paper presents a modified optimal load‐frequency controller for interconnected hydrothermal power systems. The weighting matrix of the optimal controller is sequentially modified to let the dominant energy open‐loop poles or poles in a conventional optimal feedback system be located in the desired region. The poles selected to be shifted are determined using the concept of dominant energy modes rather than those located closer to the imaginary axis. Improper pole placement can be avoided and very good system frequency and tie‐line power dynamic responses can be achieved by the proposed controller.
Optimization of a photocell
Authors: Achdou Y. , Pironneau O.
Published: July 2007

Photocells contain a silicon‐based solar energy absorbing material. An optimal design of the interface between this material and the exterior medium is desired. The problem is modelled by the Helmholtz equation. The interface is assumed to be periodic and thus only one period is considered. It is shown that the problem has a solution if the interface is not allowed to oscillate too much. An approximation of the solution is computed with the finite element method coupled with an integral Fourier method for the radiation condition. The numerical simulations show fairly large improvements in the efficiency of the photocell.
Minimum variance control for repetitive disturbances with application to active noise control
Authors: Costin Mark H.
Published: July 2007

Using minimum variance control theory, a controller is designed to reduce noise that contains a repetitive component of measurable time‐varying frequency. The particular application for which the controller is designed is the active cancellation of both road and engine noise in a vehicle passenger compartment. The controller is appropriate for this case because engine noise can be shown to be expressed as a summation of harmonically related sine waves whose frequency is determined by the engine rotational speed. An example is presented where a controller is developed for active noise control in a station‐wagon with road noise caused by striking a tyre and engine noise represented by the noise spectrum of a diesel engine. Computer simulations show that the developed controller significantly reduces the noise from both sources.
Stability margins of singularly perturbed discrete‐time systems based on state feedback and linear quadratic optimal control
Authors: Cheng Chiu‐Pin , Li Tzuu‐Hseng S. , Sun York‐Yih
Published: July 2007

Mathematical descriptions of the stability margins of discrete singularly perturbed systems are proposed. These descriptions are carried out on the basis of state feedback control and the major results are as follows: (1) the stability margins of a composite controlled system appear to be bounded by those of its subsystems; (2) the solution of the ∞‐bound for the desired stability margins is obtained; (3) some properties of linear quadratic optimal control for singularly perturbed systems are provided; (4) the effect of ϵ on the robustness is also presented under linear quadratic optimal control.
Optimal open‐loop/closed‐loop control for one‐dimensional structures with several state variables
Authors: Bruch J. C. , Sadek I. S. , Adali S. , Sloss J. M.
Published: July 2007

An optimal control problem for one‐dimensional structures described by a system of partial differential equations is formulated. Open‐ and closed‐loop control mechanisms are incorporated into the formulation and a general method of solution is presented in the context of a structural vibration problem. The expenditure of control force is restricted by penalizing a functional of the open‐loop control force in the performance index and by imposing a constraint on the magnitude of the closed‐loop control force. The optimality condition for the open‐loop control is derived by using the methods of eigenfunction expansion and variational calculus. The closed‐loop control parameters are obtained from the minimization of the energy of the system. The theory is illustrated by solving a vibration control problem for a beam undergoing torsional and flexural vibrations. Numerical results are presented in a graphical form in which the behaviours of the controlled and uncontrolled beams at different terminal times are compared. The numerical results indicate the effectiveness of the proposed control mechanism for reducing excessive vibrations as measured by the energy of the beam. The minimizing value of the closed‐loop control parameter associated with displacement feedback is shown to be a function of the terminal time.
Dynamic disturbance minimization control for discrete non‐linear stochastic systems
Authors: Azemi Asad , Yaz Engin
Published: July 2007

A dynamic feedback control scheme is proposed to reduce the effect of process and measurement disturbances of known wave‐form for a class of discrete non‐linear stochastic systems. A Lyapunovbased non‐linear filter developed previously by the authors is utilized for the estimation of the disturbance state and combined with a least‐squares‐type control action in a certainty equivalence manner for disturbance reduction. In order to illustrate the performance of the proposed dynamic disturbance rejection technique, three examples which address some important cases are provided.
Suboptimal control for bilinear systems
Authors: Ying Y. Q. , Rao M. , Sun Y. X.
Published: July 2007

Suboptimal control for bilinear systems is discussed by use of an extension of the linear‐quadratic optimal control index. The design method of this bilinear suboptimal control system is presented. Its application to the moisture control of a paper‐making process is given as an example. The simulation results show that this suboptimal control system functions very well.
Optimal advertising in growing‐stabilizing markets
Authors: Dorroh J. R. , Ferreyra Guillermo
Published: July 2007

The method of dynamic programming is used to determine the optimal synthesis of an advertising problem. The market of the product in question grows exponentially up to a time when it stabilizes at a constant value. The problem is singular and with an unbounded control. A parametrization of time is introduced to deal with these difficulties.
A linear programming approach to on‐line constrained optimal terrain‐tracking systems
Authors: Rehbock V. , Teo K. L. , Jennings L. S.
Published: July 2007

The idea of an optimal decision strategy is applied to a class of tracking problems. The resulting pointwise optimization problem is posed as a linear programming problem, in contrast to previous work where it is posed as a quadratic programming problem. A useful result concerning the convergence of the tracking error in the presence of control constraints is derived and applied to an aircraft terrain‐following system.
The determination of feedback gains for uncertain linear systems using higher‐order sensitivity minimization
Authors: Fabien Brian C.
Published: July 2007

To reduce the influence of large parameter variation on the response of linear systems, this paper considers the design of controllers that minimize the higher‐order sensitivities. Here the higher‐order sensitivities are defined as the second‐order, third‐order, etc. partial derivatives of the state and control vectors with respect to the uncertain parameter. The feedback gains are obtained by minimizing a quadratic cost function that includes state and control sensitivities of arbitrary order. The paper also presents an efficient numerical procedure for solving the resultant system of non‐linear matrix equations. The effectiveness of the approach is demonstrated by the design of an output feedback controller for an electromagnetic suspension. By comparison with standard design approaches it is shown that higher‐order sensitivity minimization can be used to reduce the deviation from the nominal trajectory caused by parameter variation.
Linear optimal control for an aircraft model
Authors: Frangos C.
Published: July 2007

A linear optimal proportional plus integral (PI) controller is designed for a lateral aircraft model such that an approximately decoupled closed‐loop step response is obtained for the roll angle and side‐slip angle while the linear optimal feedback gains are simultaneously minimized. A standard mathematical programming algorithm is employed to calculate the diagonal state weighting matrix Q such that the specifications are satisfied. The synthesis procedure consists of the iterative minimization of a functional where at each iteration step a linear optimal control problem is solved.
Stochastic adaptive control of multivariable systems with a class of amplitude‐dependent non‐linearities
Authors: Xiong Y. F. , Unbehauen H.
Published: July 2007

This paper presents a novel direct stochastic adaptive control scheme for a non‐linear multivariable system which is given by a cascade connection of a two‐segment piecewise‐linear asymmetric non‐linear matrix followed by a linear multivariable system with a general interactor matrix. An optimal control law for the non‐linear multivariable system is derived from a cost function in which the non‐linear parameter matrix of the discussed model is included. This control law results in the closed‐loop dynamic property of the non‐linear system being the same as that of its linear portion. A switching gain sequence matrix is introduced to overcome parameter estimation problems. The scheme can deal with systems whose linear portions are open‐loop unstable and/or non‐minimum phase processes. The algorithm will ensure that the closed‐loop system is globally stable and convergent.
A decomposition approach to suboptimal control of discrete‐time systems
Authors: Nardini Andrea , Piccardi Carlo , Soncini‐Sessa Rodolfo
Published: July 2007

A suboptimal controller for a class of discrete‐time systems is presented. The controller is derived by first solving ‘off‐line’ a simplified optimal control problem obtained by neglecting part of the system state and by considering a larger time step, then by solving ‘on‐line’ at each time step an optimization problem based on the results of the previously solved ‘off‐line’ problem. A simple numerical example is presented to illustrate the control scheme.
Differential dynamic programming technique for optimal control
Authors: Lin T. C. , Arora J. S.
Published: July 2007

Continuous‐ and discrete‐time differential dynamic programming (DDP) approaches to solve general optimal control problems are described and analysed. A comparison of the two approaches shows the continuous‐time approach to be more general and flexible compared with the discrete‐time approach, since it is not tied to any discretization scheme. A comparison of DDP with the non‐linear programming (NLP) approach is also given. Three structural control problems — a linear model of a space structure, a single degree of freedom non‐linear impact absorber and a non‐linear flexible beam subjected to an impulsive load — are used to numerically evaluate the continuous‐ and discrete‐time DDP approaches. Several grid sizes are used to show that the continuous‐time approach with a reasonable number of grid points is more accurate and efficient (in most cases) than the discrete‐time approach. It is therefore recommended to fully develop and evaluate the technique for the optimal control of large‐scale systems.
Terrain tracking based on optimal aim strategies
Authors: Barnard R.
Published: July 2007

This short communication discusses two recently proposed terrain‐tracking schemes, reformulates both schemes as special cases of a previously proposed optimal aim strategy, outlines a more precise and explicit continuous‐time control law based on a fixed‐point neural network, describes a more rapid and effective discrete‐time control law based on a fixed‐point iteration process, and derives criteria for matching reference models to the dynamical characteristics of individual systems.
Optimization and control of a fedbatch fermentation process
Authors: Queinnec I. , Dahhou B.
Published: July 2007

This paper describes the optimization problem of a fedbatch fermentation process for alcohol production which initially consists of minimizing a time‐optimal global criterion. Dynamic programming methods have previously allowed one to solve this global optimization problem and to deduce a local criterion to be maximized at each sampling step by using non‐linear programming techniques. It is then stated that under a few realistic constraints the optimization problem can be translated into the regulation problem of the substrate concentration in the fermentor. The optimal value is a function of a certain growth model. A control law based on the quotient between measurement and optimal value is then implemented. Simulation results and real‐life experiments validate the problem transformation.
Optimization of the protrusion shape for a couette‐type flow
Authors: Kacimov A. R.
Published: July 2007

A study is made of the longitudinal 2D viscous steady flow and heat flux between two plates. Optimal shape design problems are solved in explicit form and shown to have unique global extrema. Conformal mappings are used to bring the problems into a fixed domain and solve them as Dirichlet boundary value problems in the form of Cauchy integrals and series expansions. For the simplest problem statement the optimum is shown to coincide with the well‐known concrete dam outline of constant hydraulic gradient.
Optimal pulsing in an advertising diffusion model
Authors: Feichtinger Gustav , Novak Andreas
Published: July 2007

Empirical evidence indicates that a given moderate number of ads per year may achieve higher effect when concentrated in flights than when spread equally. In the control‐theoretic literature a few approaches have been developed for which the optimal policy is a pulsing schedule. The present communication analyses a two‐state diffusion advertising model for repeat purchasing. Recognizing the interaction between customers and potential buyers, the optimal advertising policy turns out to be a persistent periodic oscillation. This provides a further interesting example in marketing for the existence of a stable limit cycle.
Crosstalk between NF‐κB/p65 and β‐catenin/TCF4/p300 signalling pathways through alterations in GSK‐3β expression during trans‐differentiation of endometrial carcinoma cells
Authors: Saegusa M , Hashimura M , Kuwata T , Hamano M , Okayasu I
Published: July 2007

β‐Catenin/TCF4/p300 signalling loops play an important role in trans‐differentiation towards the morular phenotype of endometrial carcinomas. Crosstalk between NF‐κB and β‐catenin pathways has been proposed and we focused here on associations between these two pathways during trans‐differentiation. In normal endometrium, nuclear phosphorylated p65 (pp65), the active form NF‐κB subunit, was found to be significantly increased in the secretory phase, correlating positively with vimentin and E‐cadherin and inversely with Snail mRNA expression. On transfection of p65, vimentin, E‐cadherin, and Snail were transcriptionally altered, indicating possible roles in establishment and maintenance of the secretory phenotype. In endometrial carcinomas with morules, levels of nuclear pp65, Snail mRNA, vimentin, and cytoplasmic TNF‐α were reduced during trans‐differentiation, correlating inversely with nuclear β‐catenin. Nuclear accumulation of GSK‐3β, along with β‐catenin, was observed in morules. In cell lines, overexpression of p65 inhibited β‐catenin/TCF4‐mediated transcription, while transfection of GSK‐3β resulted in repression of TNF‐α‐induced NF‐κB activity. Moreover, nuclear GSK‐3β was increased by overexpression of β‐catenin, as well as induction of G1‐cell cycle arrest. These findings provide evidence that a shift from NF‐κB to β‐catenin signalling pathways through alterations in GSK‐3β expression may be essential for the induction of trans‐differentiation of endometrial carcinoma cells, leading to a shut‐down of mesenchymal markers. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Simulation and validation of resin flow during manufacturing of composite panels containing embedded impermeable inserts with the VARTM process
Authors: Lawrence Jeffrey M. , Frey Pierre , Obaid Ahmad Abu , Yarlagadda Shridhar , Advani Suresh G.
Published: July 2007

Modern composite materials are becoming more and more advanced as engineers are better able to take advantage of their properties. In addition to their lighter weight and net‐shape manufacturing, current interest is to make these materials multifunctional. This may require one to insert various objects into the composite to achieve a variety of different goals. It is important to understand how these embedded objects will affect both the manufacturing and the structural integrity of the component. In this work, the effects of impermeable embedded inserts on the infusion stage of vacuum‐assisted resin transfer molding (VARTM) will be explored. In VARTM, one places a distribution media on top of the preform to aid the filling as the resin will first fill the face of the preform in contact with the distribution media and will then infuse the preform in the thickness direction. However, if one has an embedded impermeable insert in the thickness direction, it will obstruct the flow in the region below the embedded object. Several case studies are conducted to understand the effect of the geometry and placement of the embedded insert and the distribution media lay out and properties on the impregnation of the resin into the fiber preform. Finally, an approach is outlined to modify the layout of the distribution media in order to ensure a complete saturation of the preform under all but the most extreme conditions. The approach is validated with experiments. POLYM. COMPOS., 28:442–450, 2007. © 2007 Society of Plastics Engineers
Characterization of composites for use in the ball‐joints of the Maeslant storm surge barrier
Authors: Van Paepegem W. , Degrieck J. , Samyn P. , De Baets P. , Van Schepdael L. , Leendertz J.S.
Published: July 2007

In 2004, the rehabilitation works of the Maeslant storm surge barrier in the Netherlands were finished. The two gates of the barrier are attached to a pivotal point on both banks. The pivotal points are designed as two large ball‐joints (10 m diameter) that must allow for both horizontal and vertical movements of the gates. Five hundred individual composite material discs provide a low friction sliding contact with the ball. Two designs for the composite material discs are discussed in this article: (i) a polyester/polyester disc with a Teflon coating and (ii) an UHMWPE (ultra‐high molecular weight polyethylene) disc with a reinforcing carbon/epoxy ring. The test methods for characterization of the composite materials are presented. It is shown that internationally standardized test methods do not provide all necessary information and that additional measurements have to be made. Based on the results of these tests, the best design has been integrated in the storm surge barrier. POLYM. COMPOS., 28:470–478, 2007. © 2007 Society of Plastics Engineers
The effect of antihypertensive drugs and drug combinations on the incidence of new‐onset type‐2 diabetes mellitus
Authors: Burke Thomas A. , Sturkenboom Miriam C. , Ohman‐Strickland Pamela A. , Wentworth Charles E. , Rhoads George G.
Published: July 2007

Purpose

To evaluate the effect of antihypertensive drugs on new‐onset type‐2 diabetes.

Methods

This was a cohort study using the UK General Practice Research Database (GPRD). Patients newly diagnosed with hypertension between 1991 and 2001, and treated with antihypertensive drugs, were included. Type‐2 diabetes mellitus was identified based on a physician diagnosis or an anti‐diabetic drug prescription. Antihypertensive treatments were classified as: ACE inhibitors (ACE‐Is), β blockers, calcium channel blockers (CCB), thiazides, all other drugs, and their combinations.

Results

A total of 2706 incident diabetes cases were identified in 98 629 hypertensive patients during 307 356 patient years (8.8/1000 patient years). New‐onset diabetes was lower for ACE‐I regimens compared with non‐ACE inhibitor regimens (HR = 0.90; 95%CI: 0.82–0.99). CCB monotherapy (HR = 1.27; 95%CI: 1.07–1.51) had an increased risk of diabetes compared with ACE‐I monotherapy. ACE‐I plus thiazide had the lowest risk of diabetes among double combinations, followed by ACE‐I plus β blocker, and ACE‐I plus CCB. Double combinations with an ACE‐I had 0.79 (95%CI: 0.67–0.92) times the risk compared with non‐ACE inhibitor combinations. The risk of new‐onset diabetes was significantly higher for β blocker plus thiazide (HR = 1.37; 1.10–1.70), CCB plus thiazide (HR = 1.44; 95%CI: 1.13–1.83), but not β blocker plus CCB (HR = 1.30; 95%CI: 0.99–1.70) compared with ACE‐I plus thiazide.

Conclusions

Antihypertensive drug combinations including an ACE‐I had a significantly lower risk of new‐onset diabetes than antihypertensive drug combinations without an ACE‐I. Copyright © 2007 John Wiley & Sons, Ltd.
Theoretical consideration on the glass transition behavior of polymer nanocomposites
Authors: Lee Kyung Ju , Lee Do Kyoung , Kim Yong Woo , choe Woo‐Seok , Kim Jong Hak
Published: July 2007

We have developed a new molecular thermodynamic model to predict the glass transition temperature (Tg) of nanocomposites consisting of polymer (1) and nanoparticle (2) based on the configurational entropy model and the Flory–Huggins theory. Four configurational entropies have been taken into account in this study: the disorientation entropy of the polymer (Sdis‐1), the confinement entropy of the nanoparticle (Scon‐2), the mixing (Smix‐12), and the specific interaction entropies (Sspe‐12) of the polymer/nanoparticle. Quantitative descriptions according to the proposed model are consistent with experimental Tg data of polymer nanocomposites. Our results demonstrate that Tg values of polymer nanocomposites can be enhanced or depressed relative to neat polymer depending on the intensity of specific interaction between polymer and nanoparticles, which is quantitatively identified by a physical parameter (γspe) in this model. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2232–2238, 2007
Propylene sorption and coordinative interactions for poly(N‐vinyl pyrrolidone‐co‐vinyl acetate)/silver salt complex membranes
Authors: Joo Seung Hwan , Kim Jong Hak , Kang Sang Wook , Jang Jyongsik , Kang Yong Soo
Published: July 2007

When poly(N‐vinyl pyrrolidone‐co‐vinyl acetate) (PVP‐co‐PVAc) containing amide and ester groups were complexed with silver salts to form silver polymer electrolyte membranes, their separation performance of propylene/propane mixtures showed the high selectivity of propylene over propane of 55 and the high mixed gas permeance of 12 GPU (1 GPU = 1.0 × 10−6 cm3(STP) cm−2 s−1 cmHg−1). The separation performance strongly depends on the composition of the copolymer: the higher concentration of PVP in the copolymer, the better separation performance was achieved. These results suggest that the amide group is more effective in facilitated propylene transport than the ester group, primarily due to the stronger interaction of the silver ions with the amide than the ester oxygens, as demonstrated by FT‐IR and FT‐Raman spectroscopies. In‐situ FT‐IR spectra upon propylene sorption also demonstrate that the interaction strength of the silver ions with the ligands is arranged: amide > CC > ester. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2263–2269, 2007
NMR‐based modeling and binding studies of a ternary complex between chicken liver bile acid binding protein and bile acids
Authors: Tomaselli Simona , Ragona Laura , Zetta Lucia , Assfalg Michael , Ferranti Pasquale , Longhi Renato , Bonvin Alexandre M. J. J. , Molinari Henriette
Published: July 2007

Chicken liver bile acid binding protein (cL‐BABP) is involved in bile acid transport in the liver cytosol. A detailed study of the mechanism of binding and selectivity of bile acids binding proteins towards the physiological pool of bile salts is a key issue for the complete understanding of the role of these proteins and their involvement in cholesterol homeostasis. In the present study, we modeled the ternary complex of cL‐BABP with two molecules of bile salts using the data driven docking program HADDOCK on the basis of NMR and mass spectrometry data. Docking resulted in good 3D models, satisfying the majority of experimental restraints. The docking procedure represents a necessary step to help in the structure determination and in functional analysis of such systems, in view of the high complexity of the 3D structure determination of a ternary complex with two identical ligands. HADDOCK models show that residues involved in binding are mainly located in the C‐terminal end of the protein, with two loops, CD and EF, playing a major role in ligand binding. A spine, comprising polarresidues pointing toward the protein interior and involved in motion communication, has a prominent role in ligand interaction. The modeling approach has been complemented with NMR interaction and competition studies of cL‐BABP with chenodeoxycholic and cholic acids. A higher affinity for chenodeoxycholic acid was observed and a Kd upper limit estimate was obtained. The binding is highly cooperative and no site selectivity was detected for the different bile salts, thus indicating that site selectivity and cooperativity are not correlated. Differences in physiological pathways and bile salt pools in different species is discussed in light of the binding results thus enlarging the body of knowledge of BABPs biological functions. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Phytoplankton dynamics in two tropical rivers with different degrees of human impact (southeast Brazil)
Authors: Soares Maria Carolina S. , Huszar Vera L. M. , Roland Fabio
Published: July 2007

Potamoplankton attracts little research attention worldwide and this also holds true in Brazil, despite its numerous river systems. The origin and maintenance of phytoplankton populations in these systems have not been well studied. We analysed biological, physical and chemical parameters of the Paraibuna and Pomba rivers to identify the main driving forces behind temporal and spatial phytoplankton patterns. Both systems are located in the southeast, the most populated region. These rivers are similar in climate and geomorphology, and have become eutrophic due to the increase in the human population of the region, especially in Paraibuna River catchments. Twelve and eleven stations were, respectively, sampled during the dry and rainy seasons in the Paraibuna and Pomba rivers. The seasonal pattern of abiotic and biotic variables was related to the increase in the discharge and dilution caused by the rainy period. However, human influences such as the presence of a reservoir and sewage inflow were important to distinguish the rivers. The phytoplankton community of Paraibuna River was influenced by Chapéu D'Uvas Reservoir, which was dominated by a toxic population of Cylindrospermopsis raciborskii. Pomba River phytoplankton was typical of the lotic tropical systems. Phytoplankton functional groups in both rivers were those commonly found in turbid and turbulent shallow lakes. Although the functional group approach was originally described for lentic environments, our data support this approach for lotic community patterns. Copyright © 2007 John Wiley & Sons, Ltd.
Modelling to extract more information from clinical trials data: On some roles for the bootstrap
Authors: Sauerbrei Willi , Royston Patrick
Published: July 2007

Despite its importance in the theoretical literature, the bootstrap appears to play a negligible role in pharmaceutical research, as will be demonstrated by a brief literature review. As will be shown by examples, the bootstrap is a useful tool in the planning and analysis of clinical trials. The first example shows that some important information required in the design of a study can best be gained by using the bootstrap. It is argued from two further examples that more information can be extracted from large clinical trials by data‐dependent modelling. This is shown by identifying a prognostic factor that may play a role as an inclusion criterion of a new study and by an interaction of a continuous predictor with treatment. To protect against erroneous conclusions from data‐dependent modelling in a multivariable context, detailed checks of the results and stability analyses should be performed by the bootstrap. To conclude, a discussion of the future of modelling and the future of the bootstrap is given.
Copyright © 2007 John Wiley & Sons, Ltd.
Effect of Molar Substitution on Rheological Properties of Hydroxypropylated Rice Starch Pastes
Authors: Chun So‐Young , Yoo Byoungseung
Published: July 2007

The steady and dynamic shear rheological properties of hydroxypropylated rice starch pastes (5%, w/w) were evaluated at different molar substitution (MS, 0.030‐0.142). The swelling power (35.5‐52.8 g/g) and solubility (8.19‐10.7%) values of the hydroxyproylated rice starches were higher than those of native rice starch (26.6 g/g and 7.78%) and increased with an increase in MS. The hydroxypropylated starch pastes at 25°C showed a pronounced shear‐thinning behavior (n = 0.33‐0.40) with Casson yield stress (σoc = 15.9‐31.7 Pa). The consistency index (K) and yield stress (σoc) values of the hydroxypropylated starch pastes were lower than those of the native starch, and increased progressively with an increase in MS. The apparent viscosity (ηa,500) obeyed the Arrhenius temperature relationship over the temperature range of 10‐55°C; the activation energies (Ea) of the hydroxypropylated starch pastes were in the range of 14.8‐18.5 kJ/mol, i.e. higher than that (14.1 kJ/mol) of the native starch. Storage (G′) and loss moduli (G′′) of hydroxypropylated starch pastes increased with an increase in MS, while tan δ (G′′/G′) values decreased, indicating that G′ rose more strongly than G′′ with increased MS.
Merging formation and current amplification of field‐reversed configuration
Authors: Inomoto Michiaki , Ono Yasushi
Published: July 2007

The merging formation of the field‐reversed configuration (FRC) has been developed in the TS‐3 merging experiment, leading us to a new scenario of FRC slow formation, heating and current amplification. Two force‐free spheromaks with opposing toroidal fields were merged together in the axial direction to form a high‐β FRC with higher efficiency than the conventional field‐reversed theta‐pinch method. This unique relaxation from the force‐free (β ∼ 0.05 − 0.1) spheromaks to the high‐β (β ∼ 0.7 − 1) FRC is attributed to the conversion of toroidal magnetic energy into ion thermal energy through the reconnection outflow. A central ohmic heating (OH) coil worked successfully to amplify the FRC plasma current by a factor of 2. Toroidal mode analysis of magnetic structure indicated that the tilting stability of the oblate FRC was provided by an ion kinetic effect. This oblate FRC is also useful as an initial equilibrium to produce a high‐βp spherical tokamak (ST) with diamagnetic toroidal magnetic field, suggesting the close relationship between FRCs and high‐βp STs in the second stable region of the ballooning mode. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Comparison with film substrates of polyimide and Ni for cantilevered magnetic actuators
Authors: Yokota Chikako , Ishiyama Kazushi , Arai Ken Ichi
Published: July 2007

This paper describes a cantilevered actuator driven by magnetostriction in a low magnetic field. The dimensions of the two‐layer actuator were 1 mm × 5 mm, and amorphous FeSiB was used as the positive magnetostrictive material. The theoretical formulas for the amount of displacement and force of the actuator were obtained. In the experiment, a nonmagnetic polyimide film material and a negative magnetostrictive Ni film material were used as the substrates. The change in the characteristics of the actuator caused by changing the substrate was examined with theoretical formulas and experiments. It is shown that the actuator with Ni as the substrate was designed to obtain the largest displacement and the largest force. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Nd–Fe–B thick films prepared at the high deposition rate of 90 µm/h
Authors: Nakano Masaki , Takeda Hiroyuki , Yamashita Fumitoshi , Fukunaga Hirotoshi
Published: July 2007

After a postannealing process, the magnetic properties of pulsed laser deposition (PLD)‐made Nd–Fe–B film magnets prepared at the deposition rate of 20–90 µm/h showed constant values, and the average values of Hc, Br and (BH)max were 1050 kA/m, 0.6 T, and 60 kJ/m3, respectively. The obtained results were comparable to those previously reported. In conclusion, it was found that a maximum deposition rate of 90 µm/h could be achieved without deterioration of magnetic and mechanical properties. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Fabrication of high‐quality two‐dimensional photonic crystals based on porous alumina
Authors: Yayoi Kazuo , Jinno Masahiko , Fujikawa Rintaro , Baryshev Alexander , Khanikaev Alexander , Shin Kwang‐Ho , Uchida Hironaga , Inoue Mitsuteru
Published: July 2007

We fabricated porous alumina templates with a well‐ordered pore array by a pre‐triggered anodization method. The arrangement of pores in the fabricated templates was set by a Ni‐dot stamper. The structure of the templates was analyzed by field emission scanning electron microscopy (FESEM), two‐dimensional Fourier transformation of FESEM images and optical means. It was found that the porous alumina templates have a high‐quality, extended, two‐dimensional hexagonal lattice, which can be used in the fabrication of two‐dimensional magnetophotonic crystals (2D‐MPCs). © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Synthesis and characterization of long gold nanorods
Authors: Liu Ru‐Shi , Chen Hao Ming , Hu Shu‐Fen
Published: July 2007

A new approach to fabricate long gold nanorods by controlling the volume of the growth solution is reported. Shapes ranging from fusiform nanoparticles to 1D rods were observed to evolve. Increasing the growth solution can control the length of the nanorods. The length of the rods could be extended to 2 µm, and nanorods with aspect ratios of up to ∼70 could be obtained. Moreover, X‐ray absorption spectroscopy (XAS) was used to elucidate the growth mechanism of gold nanorods. The gold ions were directly reduced to gold atoms by ascorbic acid during the reaction, and the gold atoms were deposited on the surface of gold seeds, which were introduced into the reaction. Extended X‐ray absorption fine structure (EXAFS) confirmed the growth of gold and the environment around Au atoms during the reaction. XAS is expected to have wide applications in the growth of gold and other related materials. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
A 5‐MHz AT‐cut quartz crystal oscillating circuit functioning in 350 nA
Authors: Sato Tomio , Tanaka Hirokazu , Ehara Kei , Kanno Yoshinori
Published: July 2007

An oscillating circuit functioning at ultra low power (350 nA) for a 5‐MHz AT‐cut quartz crystal oscillator was investigated. This circuit has a resistance between the power terminal of the CMOS‐IC and the power supply, and another between the earth terminal of the CMOS‐IC and the ground (GND). These resistances discourage an inrush of current, and set a gain (gm) necessary for oscillating the circuit at minimum. The developed circuit is quite simple, but enables driving at once‐unthinkable, low power (below 1 µA). © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Noncontact measurement of deep tissue absorption coefficient using Spatially Resolved Near‐Infrared Spectroscopy
Authors: Niwayama Masatsugu , Murata Hideaki , Sone Shingo , Shinohara Shigenobu
Published: July 2007

We examined the influence of probe‐tissue distance on the relationship between the deep tissue absorption coefficient and the spatial profile of light intensity by Monte Carlo simulation and in vivo experiments, using noncontact spatially resolved near‐infrared spectroscopy (SRS). These results suggest that noncontact SRS can be reliably used for noncontact measurement of the absorption coefficient and oxygen saturation of deep tissues. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Lead induced malformations in embryos of the African catfish Clarias gariepinus (Burchell, 1822)
Authors: Osman Alaa G. M. , Wuertz Sven , Mekkawy Imam A. , Exner Hans‐Jürgen , Kirschbaum Frank
Published: July 2007

The effect of lead exposure (100, 300, and 500 μg/L lead nitrate) on embryos of the African catfish Clarias gariepinus were examined by gross morphology and histopathology. Exposition to lead nitrate caused a progressively longer delay in hatching and also reduced the percentage of embryos, which successfully completely hatch from 75% in the control group to 40% in the group exposed to 500 μg/L lead. Categories of gross morphological abnormalities comprised four major ones (irregular head shape, pericardial edema, yolk sac edema, and notochordal defect) and two minor deformations (finfold defect and reduction of pigmentation). The frequencies of recorded morphological malformations increased significantly (P < 0.05) with increasing lead concentration in all stages. Four histopathological categories comprising notochordal defect, gill malformation, eye malformation, and detached skin were recorded. All these malformations were recorded only in the embryos exposed to 300 and 500 μg/L lead. The degrees of histological lesions increased with increasing lead concentration and with length of exposure time. Mean concentrations of lead in the whole embryos were measured and the lowest concentrations of lead were recorded in the control groups (0.3–1.0 μg/g wet wt). Accumulated lead increased significantly (P < 0.05) with increasing dose in all stages. Accumulation of lead in the chorion suggests that the chorion acts as an effective barrier protecting the embryo. Low impact of lead on prehatching stages may be related to both the protective capacity of the chorion and the ability of the perivitelline fluid to concentrate lead. The present results show that (i) lead toxicity was dosage dependent and become evident in gross morphological malformations, followed by histopathological changes, and (ii) early life stages of the African catfish C. gariepinus are a very sensitive bioassay for aquatic lead pollution. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 375–389, 2007.