bluuebunny/crossref_metadata_2025 huggingface dataset:
Strategy of evasion from many pursuers
Authors: Zak V. L.
Published: July 2007

A differential game of evasion with many participants (a game of kind in the terminology of Isaacs1) is considered. One controlled object (the evader) seeks to avoid contact with each of several pursuers. The motion of the evader is subject to a phase constraint. An efficient method (up to the explicit formulae) of constructing the evader's strategy is proposed. This strategy ensures evasion on the infinite time interval and the fulfilment of the phase constraint. The evader's control corresponding to this strategy is always a piecewise‐programme function of time, and the number of programme pieces is finite (there is an upper estimate for this number). There is a lower estimate for the minimal distance between the evader and the pursuers.
Modelling and control of a rotary crane with a flexible joint
Authors: Yoshimoto Tadashi , Sakawa Yoshiyuki
Published: July 2007

A dynamical model is derived for the control of a rotary crane, which has a flexible joint and makes three kinds of motion (rotation, load hoisting and boom hoisting) simultaneously. The goal is to transfer a load to a desired place in such a way that at the end of the transfer the swing of the load decays as quickly as possible. A new open‐loop plus feedback control scheme is proposed.
Optimal inventory policy with partial backordering
Authors: Wee H. M. Moses
Published: July 2007

This paper formulates an inventory stocking policy with partial backordering. An implicit assumption in most inventory control models is that when there is a shortage, either complete backordering or complete lost sales is assumed. Such an assumption is not always tenable in view of the different responses by customers during stockout. Others who assume a fixed ratio of backordering and lost sales encounter the complication of a non‐convex cost function. When the cost function is non‐convex, the equation formulated is unstable; hence the optimal value is rather tedious to find. In this paper the fraction of backordering and lost sales is constrained so that convexity can be assured by means of the Hessian matrix. In this way the search for the optimal solution is simplified.
A chebyshev technique applied to a controlled nuclear reactor system
Authors: Van Dooren R.
Published: July 2007

The optimal control of a nuclear reactor system with a single group of delayed neutrons is studied by applying a numerical method based on the expansion of the unknown functions in Chebyshev series. It is shown how the given system dynamics, the initial and final conditions and the performance index are replaced by certain approximate versions. Several practical cases are given in which different control strategies are considered.
Optimal control of linear discrete systems via hahn polynomials
Authors: Hwang Chyi , Chen Chyi‐Tsong , Shih Yen‐Ping
Published: July 2007

This paper presents a method of finite series expansion using Hahn polynomials for the finite time optimal control of linear discrete time systems with a quadratic performance index. The method converts the discrete two‐point boundary value Euler—Lagrange difference equations into a set of linear algebraic equations. As a result, the computation is simple and straightforward.
Singular perturbation method applied to the closed‐loop discrete optimal control problem
Authors: Krishnarayalu M. S.
Published: July 2007

An improved singular perturbation method for the singularly perturbed, closed‐loop discrete optimal control problem with two terminal boundary layer correction series is presented.
A multidimensional optimal stopping‐time problem, with time‐average criterion
Authors: Sun Min
Published: July 2007

An optimal stopping‐time problem for a diffusion process absorbed at the boundary of a bounded domain inRd(d le 1) is considered. The cost criterion is of time‐average type and may be regarded as a version of the Gittins index. We characterize the value function and construct an optimal stopping policy using dynamic programming. Two numerical algorithms are used to solve two test problems inR1andR2.
Control of a long‐line‐type plant
Authors: Szymkat Maciej , Görecki Henryk , Popek Leslaw
Published: July 2007

This paper presents an approach to the feedback loop controller design problem for plants described by linear partial differential equations of a long‐line type. The classical frequency domain technique called ‘the optimal modulus criterion’ is applied. The different plant cases are classified and the corresponding recurrence formulae for derivatives of the transfer function inverse are derived. The applicability of the presented technique is discussed with particular emphasis on stability and performance aspects. The conclusions for different types of controllers are illustrated with several examples. This analysis uses an originally developed computer package.
An exercise in modelling of consumption, import and export of an exhaustible resource
Authors: Sethi Suresh , Sorger Gerhard
Published: July 2007

In this paper we analyse a control‐theoretic model of a country possessing a finite amount of a non‐renewable resource. The country can both consume the indigenous resource and export it. Moreover, a substitute for the indigenous resource is available at a given backstop price. We obtain the optimal consumption, export and import policy for the country.
Stochastically optimal advertising policies under dynamic conditions: The ratio rule
Authors: Raman Kalyan
Published: July 2007

There has been considerable debate among marketing researchers about the optimality of popularly used advertising policies. In particular, the ratio rule has aroused much interest. This paper analyses its optimality under the expected profit maximization criterion for a general class of models. The optimality of the ratio rule extends to the stochastic case provided that the conditions which ensure its optimality for the deterministic case are enlarged by an additional restriction. This additional restriction has the effect of transforming the stochastic evolution of goodwill and sales to log‐normal processes. Advertising dynamics, the nature of the response function and unexplained error variance all interact to determine whether the ratio rule is exactly optimal, approximately optimal or not optimal at all.
Approximate parallel controllers for discrete stochastic weakly coupled linear systems
Authors: Shen Xuemin , Gajic Zoran
Published: July 2007

The global Kalman filter of linear weakly coupled discrete systems is exactly decomposed into separate reduced‐order local filters via the use of a decoupling transformation. The approximate parallel controllers, up to an arbitrary degree of accuracy, are derived by approximating coefficients of the optimal control law. The proposed method allows parallel processing of information and reduces both off‐line and on‐line computational requirements. A real‐world example demonstrates the efficiency of the proposed method.
On mimo optimal preview tracking control for known trajectory models
Authors: Pak H. A. , Shieh R.
Published: July 2007

A class of discrete time feedforward tracking controllers is presented for linear multivariable plants subjected to time‐varying exogenous inputs with known models. The controller design is based on linear quadratic optimization techniques and the augmented system approach. The optimal controllers use state feedback for regulation purposes. For the tracking objective the future set‐points along the reference trajectory vector are used. Necessary and sufficient conditions for the existence of an optimal feedforward solution are presented in terms of the relationships between the eigenvalues of the closed‐loop system and those of the trajectory models. For illustration a numerical example is included which is based on a dual‐stage positioning carriage modelled as a linear multivariable plant.
Further results on the optimal regulation of spacecraft angular momentum
Authors: Bourdache‐Siguerdidjane Houria
Published: July 2007

A direct analytical solution of angular velocities is given for regulating the angular momentum of a spacecraft using reaction jets only. The solution, which appears to be new, may be written down in terms of characteristic values and characteristic vectors. These values and vectors satisfy an algebraic non‐linear equation.
An algorithm for optimal scheduling of a class of cascade water supply systems
Authors: Brdys M. A.
Published: July 2007

The problem of determining overall optimized control schedules for a class of cascade water supply systems containing only fixed speed pumps is examined. The system control is by nature an on‐off type. The optimal scheduling problem can be formulated as dynamical optimal control problems with purely discrete symbols, discrete controls and also with continuous intermediate variables interrelated in a highly non‐linear way. An efficient problem solver is proposed. Its high efficiency is achieved by exploiting, through a suitable decomposition, certain structural properties of the problem. Lagrange relaxation is applied in order to break down the time structure of discrete control variables. The decomposition also enables consideration of mixed integer optimization on purely static grounds. The dynamical optimization constitutes only that part of the solver which deals with entirely continuous variables. There is a duality gap in the problem. However, certain, but not complete, information obtained through solving the dual problem (dual optimal information) is close to that which corresponds to the true (primal) optimal solution. This is an important property of the scheduling problem, which together with the problem structure creates a basis for the solver design.
Robust pole assignment in a specified region using output feedback
Authors: Oh Myungho , Gu Da‐Wei , Spurgeon Sarah K.
Published: July 2007

An output feedback pole assignment method is presented which seeks to achieve a robust solution where the assigned poles are as insensitive as possible to perturbations in the closed‐loop system. The freedom available to obtain a robust solution is realized by assigning poles not to exact locations but within specified regions of the complex plane. The problem is formulated as a non‐linear programming problem with a set of non‐linear constraints of matrix‐valued functions as well as a set of linear constraints. A numerical algorithm is presented in two forms and the results obtained are compared with those generated from other algorithms for a series of test examples taken from the literature.
Decomposition method for solving kalman filter gains in singularly perturbed systems
Authors: Shen Xuemin , Rao Ming , Ying Yiqun
Published: July 2007

In this paper a decomposition method is introduced for the solution of the optimal Kalman filter gains in singularly perturbed systems by solving two reduced‐order linear equations. The decomposition is achieved via the use of the Chang transformation, which is applied to the Hamiltonian matrix of the singularity perturbed Kalman filter. Since the decoupling transformation can be obtained up to an arbitrary degree of accuracy at very low cost, this approach produces an efficient numerical method for obtaining the Kalman filter gains. A numerical example is given to demonstrate the efficiency of the method.
Autopilot design using mixed H2 and H∞ optimal control
Authors: Sparks Andrew , Yeh Hsi‐Han , Banda Siva
Published: July 2007

An autopilot for a transport aircraft is designed using mixed H2 and H∞ optimal control. The control law design technique allows real parameter uncertainty to be accounted for in the design process. The autopilot consists of an inner loop that controls aircraft heading in response to external commands and an outer loop that tracks a localizer beam so that the aircraft is properly aligned with the runway for landing. The problem formulation and the robust control law design technique allow a wide range of performance and robustness requirements to be met. Analysis of the closed‐loop system shows the controller performance and robustness for a number of flight conditions through two separate approach profiles.
Existence of optimal control for non‐linear systems with an implicit derivative
Authors: Dauer J. P. , Balachandran K.
Published: July 2007

The existence of an optimal control for non‐linear systems having an implicit derivative with quadratic performance is proved. The results are established through the notions of condensing map and measure of non‐compactness of a set and using a fixed point theorem due to Sadovskii.
Numerical solution of time‐delayed optimal control problems with terminal inequality constraints
Authors: Lee Llan Y.
Published: July 2007

In this short communication we consider an approximation scheme for solving time‐delayed optimal control problems with terminal inequality constraints. Time‐delayed problems are characterized by variables x(t ‐ τ) with a time‐delayed argument. In our scheme we use a Páde approximation to determine a differential relation for y(t), an augmented state that represents x(t ‐ τ). Terminal inequality constraints, if they exist, are converted to equality constraints via Valentine‐type unknown parameters. The merit of this approach is that existing, well‐developed optimization algorithms may be used to solve the transformed problems. Two linear/non‐linear time‐delayed optimal control problems are solved to establish its usefulness.
Stability of distributed estimators for linear stochastic systems
Authors: McCullough Claire L. , Birdwell J. D. , Lenhart S. M.
Published: July 2007

In this paper we examine the stability of estimators on the infinite time horizon in the case where mismatch exists between the true system and the system model assumed by the filters. A counterexample is given to show that standard stability requirements on the true system and the filters are not sufficient to guarantee that covariance of the error between the actual state and the estimate remains finite in the limit. Sufficient conditions for uniformly bounded error covariance are presented and in a special case, necessary and sufficient conditions are given. These will ensure that a filter is implementable and will remain stable over the infinite time horizon. We also show that an asymptotically stable system will not necessarily have finite state covariance in the limit as t → ∞, and give the necessary and sufficient conditions to assure boundedness of the covariance.
Identification of rudder—yaw and rudder—roll steering models by using recursive prediction error techniques
Authors: Zhou Wei‐Wu , Cherchas Dale B. , Calisal Sander
Published: July 2007

Linear and non‐linear recursive prediction error (RPE) methods have been employed for the purpose of identification of the dynamics of ship rudder—yaw and —roll motions. The evaluations of the goodness of model structures have been carried out by comparing simulated outputs from the identified model with real measurements. In the linear case Nomoto's first‐order model has been initially considered for the transfer functions between rudder—yaw and —sway, with a second‐order model for rudder—roll with coupling effects considered only between sway—yaw and —roll. Identification results have shown that such a model is not appropriate. Changing the model to second‐order between rudder—sway and —yaw and further considering the coupling effects between roll angle—sway and —yaw shows that a significant improvement is achieved, while the coupling effect between yaw and roll appears negligible. In the nonlinear case effects due to various non‐linear terms have been studied with the non‐linear RPE algorithm.
Further development of an approximate loop transfer recovery methodology for fixed order dynamic compensator design
Authors: Byrns Edward V. , Calise Anthony J.
Published: July 2007

This paper further develops a methodology for designing fixed order compensators. The formulation uses an approximate loop transfer recovery (LTR) method to achieve performance and stability subject to a disturbance and unstructured uncertainty at either the plant input or the plant output. The approximate LTR methodology has the advantage that the quadratic performance index weighting matrices are uniquely defined. To reduce sensitivity to real parameter uncertainty, the performance index is modified to include a penalty on the closed‐loop sensitivity dynamics. The formulation avoids the explicit introduction of sensitivity states into the performance index and thus does not increase the overall dimension of the problem. An example design for the coupled mass benchmark control problem is provided to demonstrate this methodology.
New performance bounds of continuous‐time LQ systems with uncertain parameters
Authors: Zhang X. F. , Luo J. S. , Johnson A.
Published: July 2007

In this short communication we present new upper and lower performance bounds of LQ (linear—quadratic) systems with time‐varying parametric uncertainties. These new performance bounds improve on those proposed by Wang and Kuo by giving more accurate measures of performance robustness. We use the same example as that used by Wang and Kuo to show that the improvements are substantial.
Discrete time lq design from the viewpoint of the inverse optimal regulator
Authors: Mehdi D. , Darouach M. , Zasadzinski M.
Published: July 2007

In this communication a new design method for the discrete‐time LQ regulator based on the solution of the inverse optimal regulator is presented. The main feature of the method is that it requires no Riccati solution in addition to having a number of tuning parameters which help to shape a desirable response of the closed‐loop system.
An application of optimal control theory to the trajectory tracking of rigid robot manipulators
Authors: Grabbe M. T. , Dawson D. M.
Published: July 2007

In this paper optimal control theory is applied to the trajectory tracking problem for a rigid robot manipulator. First a stability result is developed showing the relationship between optimal control theory and the global exponential stability of a class of second‐order non‐linear systems. Next this class of nonlinear systems is shown to contain the trajectory tracking error dynamics for a rigid robot manipulator when using a modified computed torque controller with an auxiliary input. Finally the stability result is applied to the tracking error dynamics to determine the auxiliary input to the robot controller. The result is a non‐linear feedback control law which provides exponentially stable position and velocity tracking for a rigid robot manipulator without complete feedback linearization of the robot dynamics.
Analysis of optimal controls for a mathematical model of tumour anti‐angiogenesis
Authors: Ledzewicz U. , Schättler H.
Published: July 2007

Anti‐angiogenic therapy is a novel treatment approach for cancer that aims at preventing a tumour from developing its own blood supply system that it needs for growth. In this paper we consider a mathematical model where the endogenous stimulation term in the dynamics is taken proportional to the number of endothelial cells. This system is an example from a class of mathematical models for anti‐angiogenic treatment that were derived from a biologically validated model by Hahnfeldt, Panigrahy, Folkman and Hlatky. The problem how to schedule a given amount of angiogenic inhibitors to achieve a maximum reduction in the primary cancer volume is considered as an optimal control problem and it is shown that optimal controls are bang‐bang of the type 0a0 with 0 denoting a trajectory corresponding to no treatment andaa trajectory with treatment at maximum dose along that all inhibitors are being exhausted. Copyright © 2007 John Wiley & Sons, Ltd.
Influence of fiber orientation on high stress wear behavior of sisal fiber‐reinforced epoxy composites
Authors: Chand Navin , Dwivedi U. K.
Published: July 2007

Sisal fiber‐reinforced epoxy composites having three different fiber orientations, namely LL, LT, TT mentioned in the text were prepared and tested for their high stress abrasive wear behavior. Effect of fiber orientation, sliding distance, and load on abrasive wear of sisal–epoxy composites have been determined. Wear data of composites have been compared with the pure epoxy. Incorporation of fibers decreases the wear rate of epoxy resin, which varies with the fiber orientation. Wear rate in case of TT composite is found minimum as compared to other two composites. Wear rate follows the following trend, WTT < WLT < WLL. Owing to minimum exposed area of fiber to the sliding asperities, lowest wear rate occurs in the case of TT composite. Increase of load and sliding distance increases the wear volume in all the composites, because of the progressive loss of material. Wear mechanism has been discussed by using SEM micrographs of the worn surfaces. POLYM. COMPOS., 28:437–441, 2007. © 2007 Society of Plastics Engineers.
Fluorinated aramid fiber reinforced polypropylene composites and their characterization
Authors: Maity J. , Jacob C. , Das C.K. , Kharitonov A.P. , Singh R.P. , Alam S.
Published: July 2007

Polymer fibers are one of the main substances used for the reinforcement of plastic composites. Surface modification of aramid fiber was performed by direct fluorination. The crystallinity and the decomposition temperature of the modified fiber were increased. Scanning electron microscope shows that the roughness increases in the modified fiber. Composites were prepared by using modified and unmodified fibers. It was shown that the mechanical and thermal properties increase for modified fiber reinforcing composites. To reduce the fiber degradation or breakdown, composites were prepared by solution casting method. POLYM. COMPOS., 28:462–469, 2007. © 2007 Society of Plastics Engineers
Melting and crystallization behavior of polyhedral oligomeric silsesquioxane‐capped poly(ε‐caprolactone)
Authors: Ni Yong , Zheng Sixun
Published: July 2007

In this study, we investigated the melting and crystallization behavior of polyhedral oligomeric silsesquioxane (POSS)‐capped poly(ε‐caprolactone) PCL with various lengths of PCL chains by means of X‐ray diffraction and differential scanning calorimetry. This organic–inorganic macromolecule possesses a tadpole‐like structure in which the bulky POSS cage is the “head” whereas PCL chain the “tail”. The novel organic–inorganic association result in the significant alterations in the melting and crystallization behavior of PCL. The POSS‐terminated PCL displayed the enhanced equilibrium melting points compared to the control PCL. Both the overall crystallization rate and the spherulitic growth rate of the POSS‐terminated PCLs increased with increasing the concentration of POSS (or with decreasing length of PCL chain in the hybrids). The analysis of Avrami equation shows that the crystallization of the POSS‐terminated PCL preferentially followed the mechanism of spherulitic growth with instantaneous nuclei. It is found that the folding free energy of surface for the POSS‐terminated PCLs decreased with increasing the concentration of POSS. It is found that the folding free energy of surface for the POSS‐terminated PCLs decreased with increasing the concentration of POSS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2201–2214, 2007
Silica nanoparticle dispersions in homopolymer versus block copolymer
Authors: Lan Qiang , Francis Lorraine F. , Bates Frank S.
Published: July 2007

Silica nanoparticles (17 ± 4 nm in diameter) were modified by grafting polystyrene chains to the surfaces using atom transfer radical polymerization (ATRP). The molecular weight of the grafted chains ranged from 8 to 48 kDa. These modified nanoparticles were mixed in solution with poly(styrene) homopolymer (18–120 kDa) and symmetric poly(styrene‐b‐butadiene) (PS‐PB) diblock copolymer (34–465 kDa) and the states of dispersion in the dried composites were characterized by transmission electron microscopy (TEM). In the so‐called wet brush limit, when the graft molecular weight equals or exceeds the matrix value, the silica particles form a uniform random dispersion in poly(styrene). Increasing the homopolymer matrix, molecular weight above the graft value results in particle clustering and macroscopic‐phase separation. Mixtures of the lamellar forming block copolymer and nanoparticles exhibit a very different trend, with particle clustering at the lower PS‐PB molecular weights and dispersion at the highest value. This latter finding is rationalized on the basis of packing constraints associated with lamellar order and the effective particle dimensions, and the degree of solvation at ordering, both of which favor higher molecular weight block copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2284–2299, 2007
Surface reconstructions of II‐VI compound semiconductor surfaces
Authors: Kumpf Christian , Weigand Wolfgang , Müller Arthur , Wagner Joachim , Wagner Veit , Bach Peter , Schmidt Georg , Molenkamp Laurens W. , Geurts Jean , Umbach Eberhard
Published: July 2007

The surface structures of two model systems in the field of II‐VI semiconductors – the ZnSe(001)‐c(2×2) and the BeTe(001)‐2×1 surface – are derived from spot‐profile analysis low‐energy electron diffraction and surface X‐ray diffraction (SXRD). For the first, a Zn‐vacancy model could be unambiguously confirmed by the comparison of our SXRD data with density functional theory calculations. The BeTe surface consists of [1$ \bar 1 $0]‐oriented Te dimers inducing a large amount of surface strain. This causes pronounced vertical and lateral atomic displacements in the underlying BeTe bilayers which effectively relieve the surface strain. The experimentally derived atomic geometry is in very good agreement with the results of density functional theory calculations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Single‐Walled Carbon‐Nanotube Spectroscopic and Electronic Field‐Effect Transistor Measurements: A Combined Approach
Authors: Kauffman Douglas R. , Star Alexander
Published: July 2007

Spectroscopic and electronic field‐effect transistor measurements reveal complimentary information about molecular interactions with single‐walled carbon nanotubes (SWNTs). Here we demonstrate how these two complimentary techniques can be combined to further understand electronic modifications of the SWNTs. The complimentary nature of these techniques stems from the perturbation of the electronic structure of SWNTs upon electronic interaction with an electron‐donating, or ‐accepting species.
Physicochemical Characterization and Application of Yam (Dioscorea cayenensis‐rotundata) Starch as a Pharmaceutical Excipient
Authors: Zuluaga María‐Fernanda , Baena Yolima , Mora Claudia‐Elizabeth , D'León Luisa‐Fernanda Ponce
Published: July 2007

Yam starch from Dioscorea cayenensis‐rotundata complex was isolated and characterized by scanning electron microscopy (SEM), particle size analysis, X‐ray diffraction, differential scanning calorimetry (DSC), compaction and rheology, and compared to maize (Zea mays) and potato (Solanum tuberosum) starches. Yam starch exhibited a log‐normal distribution of flattened ovoid shaped granules with a mean particle size of 25 µm. X‐ray diffraction showed a C‐type crystalline pattern with the degree of relative crystallinity estimated to be 34%. DSC analysis suggests that the crystalline regions in yam starch are thermally and structurally more stable as in maize and potato. Irrespective of the relative humidity (39, 67, 78% R.H.) yam starch exhibited higher moisture uptakes than maize starch and lower than potato. Intermediate values of swelling power and amylose leaching were obtained for yam as compared to maize and potato. Compaction properties of yam and potato starches were similar. However, compacts from yam presented a relatively lower tensile strength. Aqueous starch systems (4%) of yam and maize starches showed analogous shear‐thinning (pseudo‐plastic) behavior suitably described by the power‐law model. These results support the potential use of yam starch as excipient comparable to potato starch in pharmaceutical solid forms and as thickening agent similar to maize in pharmaceutical applications.
Resistive switching effect in metal/insulator/metal heterostructures and its application for non‐volatile memory
Authors: Akinaga H. , Shima H. , Takano F. , Inoue I. H. , Takagi H.
Published: July 2007

This paper presents two types of resistive switching effects observed in metal/insulator/metal heterostructures: one is the forced‐switch type, and the other is the memory‐switch type. The former was observed in metal/semi‐insulating GaAs hybrid structures. The nonlinear resistive switch showed a strong magnetic field dependence at room temperature. The latter, described in this report, appears in the Pt/Co oxide/Pt capacitor structures. The resistive switch showed bistability, which is certainly a phenomenon with great promise of application to nonvolatile solid state electronic memory. For both cases, the recent experimental evidences show that the electronic state of the interface between the metal electrode and the insulator plays a crucial role in the resistive switching effect. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
PLZT films prepared by aerosol deposition and their birefringence evaluation
Authors: Yamaguchi Takashi , Shin Kwang‐Ho , Lim Pang‐Boey , Uchida Hironaga , Inoue Mitsuteru
Published: July 2007

Pb0.91La0.09(Zr0.65Ti0.35)O3 (PLZT) films were prepared by the aerosol deposition method (ADM) and their optical and electro‐optic (EO) properties investigated for application to hologram optical switch. We found that a higher transmittance of the films was obtained with smaller particles. The transmittance of the PLZT film deposited with particles of 0.2 µm average diameter, the smallest size in this experiment, was nearly 100%, showing that the PLZT film deposited by aerosol deposition can be applied to practical optical devices. We evaluated the birefringence shift of the film to make the EO performance clear. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Toxic cyanobacterial blooms in reservoirs under a semiarid mediterranean climate: The magnification of a problem
Authors: Naselli‐Flores Luigi , Barone Rossella , Chorus Ingrid , Kurmayer Rainer
Published: July 2007

Sicilian reservoirs constitute the most important water resources available on the island. During summer 2001, the intense water utilization of Lake Arancio reservoir reduced the water level significantly, which coincided with the formation of intense blooms formed by the microcystin (MC)‐producing cyanobacterium Microcystis aeruginosa. During summer 2003, Lake Arancio was continuously filled and the vertical stratification of the water column was maintained resulting in five to sixfold lower cell numbers of M. aeruginosa. For both years, a significant relationship between MC net production and Microcysytis cell growth was observed, implying that Microcystis cell numbers can be used to infer MC concentrations in water. Unexpectedly, dense blooms of the MC‐producing cyanobacterium Planktothrix rubescens occurred during winter 2005/2006 in the reservoirs Lake Pozzillo, Prizzi, Nicoletti, and Garcia but have not been reported earlier. In this season, MC concentrations higher than those recorded in summer were measured, implying that monitoring of Mediterranean drinking water reservoirs needs to be intensified during winter, a season usually considered to be less prone to the formation of cyanobacterial blooms. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 399–404, 2007.
Effects of perchlorate on sodium‐iodide symporter and pendrin gene expression in deer mice
Authors: Cheng Qiuqiong , Smith Ernest E. , Liu Fujun , Gentle Angela , Hooper Michael J. , Anderson Todd A.
Published: July 2007

Effects of perchlorate on sodium‐iodide symporter (NIS) and pendrin gene expression in deer mice kidney and stomach were investigated. This was accomplished by isolating a partial cDNA sequence of deer miceNISgene of 425 bps, and quantitatively analyzingNISmRNA expression in various deer mouse tissues. The highestNISexpression level was in the stomach, followed by testes, brain, and large intestine; very low expression ofNISwas observed in the lung, kidney, heart, and liver. Exposure to perchlorate through drinking water for 28 days did not significantly increaseNISgene expression in the kidney and stomach, and pendrin gene expression in the kidney. In a depuration experiment in which deer mice were exposed to perchlorate for 8‐h followed by an 88‐h depuration period, no significant difference was observed between the low and high exposure groups in terms ofNISor pendrin gene expression in the kidney or stomach at the end of the experiment. Furthermore, no significant linear relationship was observed between gene expression (eitherNISor pendrin) in the kidney and perchlorate mass excreted via urine at day 28, average daily excretion, or total excretion mass over the 28 day exposure. Several factors could influence the effect of perchlorate exposure on NIS and pendrin gene expression in the stomach and kidney, including (1) pre‐exposure to trace perchlorate through food and water perhaps resulting in adaptation (or tolerance) in these animals; (2) metabolism of perchlorate in deer mice causing only 46–61% perchlorate excreted into urine. It is also possible that there is no effect of perchlorate exposure and/or urinary excretion on NIS and pendrin gene expression, particularly in the kidney. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 390–398, 2007.
The alteration of Microcystis aeruginosa biomass and dissolved microcystin‐LR concentration following exposure to plant‐producing phenols
Authors: Dziga Dariusz , Suda Magdalena , Bialczyk Jan , Czaja‐Prokop Urszula , Lechowski Zbigniew
Published: July 2007

Plant‐producing phenols could strongly inhibit the growth of toxic cyanobacteria genera, but the ecological consequences of this action are still unknown. In this work, the activity of selected phenols in relation to the strain Microcystis aeruginosa was investigated. We have found that the mechanism of the growth inhibition could involve both the inhibition of the photosynthetic system and the alkaline phosphatase activity. The excretion of a high amount of microcystin‐LR to the environment was observed as a final result of the application of phenols to the cyanobacterial culture. This finding suggests that first of all an algicidal effect of phenols was probably the reason of the cyanobacterial biomass decreasing. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 341–346, 2007.
Summer learning and its implications: Insights from the Beginning School Study
Authors: Alexander Karl L. , Entwisle Doris R. , Olson Linda Steffel
Published: July 2007

There is perhaps no more pressing issue in school policy today than the achievement gap across social lines. Achievement differences between well‐to‐do children and poor children and between disadvantaged racial and ethnic minorities and majority whites are large when children first begin school, and they increase over time. Despite years of study and an abundance of good intentions, these patterned achievement differences persist, but who is responsible, and how are schools implicated? The increasing gap seems to suggest that schools are unable to equalize educational opportunity or, worse still, that they actively handicap disadvantaged children. But a seasonal perspective on learning yields a rather different impression. Comparing achievement gains separately over the school year and the summer months reveals that much of the achievement gap originates over the summer period, when children are not in school. The authors review Beginning School Study research on differential summer learning across social lines (that is, by family socioeconomic level) and its implications for later schooling outcomes, including high school curriculum placements, high school dropout, and college attendance. These studies document the extent to which these large summer learning differences impede the later educational progress of children of low socioeconomic status. Practical implications are discussed, including the need for early and sustained interventions to prevent the achievement gap from opening wide in the first place and for high‐quality summer programming focused on preventing differential summer learning loss.
Summer library reading programs
Authors: Fiore Carole D.
Published: July 2007

Virtually all public libraries in the United States provide some type of summer library reading program during the traditional summer vacation period. Summer library reading programs provide opportunities for students of many ages and abilities to practice their reading skills and maintain skills that are developed during the school year. Fiore summarizes some of the research in the field and relates it to library programs and usage by students. Several traditional and innovative programs from U.S. and Canadian libraries are described. She concludes with a call for further research related to summer library reading programs.
Detection of Argan Oil Adulteration Using Quantitative Campesterol GC‐Analysis
Authors: Hilali Miloudi , Charrouf Zoubida , Soulhi Abd El Aziz , Hachimi Larbi , Guillaume Dominique
Published: July 2007

Detection of edible oil adulteration is of utmost important to ensure product quality and customer protection. Campesterol, a sterol found in seed oils, represents less than 0.4% of argan oil total sterol content. Quantitative analysis of campesterol by gas chromatography of argan oil and of a mixture of argan oil and readily commercially available vegetable oils, consecutively with sterol separation, was carried out. Our study clearly demonstrated that determination of the campesterol level in argan oil (or oil presented as argan oil) can be proposed as the major analysis method to assess unambiguously argan oil purity up to 98%.
Fatty Acid Composition and Oil Yield in Fruits of Five Arecaceae Species Grown in Cuba
Authors: Rodríguez‐Leyes Eduardo A. , Canavaciolo Víctor L. González , Delange David Marrero , Enríquez Abel R. Sgambelluri , Fajardo Yuliamny Adames
Published: July 2007

The present study targeted the whole‐fruit oil yield and fatty acid composition from five of the most abundant Arecaceae species grown in Cuba. The oil yields (% dry weight), determined by the Soxhlet extraction technique with hexane, were 25.5, 5.3, 6.9, 5.4, and 6.4% for Roystonea regia, Colpothrinax wrightii, Sabal maritima, Sabal palmetto and Thrinax radiata, respectively. The free fatty acid (FFA) content varied from 2.7 to 6.8%. Fatty acid (FA) profiles of the oils indicated that lauric acid (13.7–44.4%), myristic acid (9.4–22.4%) and palmitic acid (9.2–17.1%) as major saturated FA; whereas oleic acid (9.6–42.7%) and linoleic acid (9.3–17.0%) as major unsaturated FA. R. regia fruit seemed the most promising among Arecaceae grown in Cuba because of its high oil yield and low oil FFA content.
The treatment of Wegener's Granulomatosis with immunosuppressive-cytotoxic drugs
Authors: Froud P. J. , Henderson A. H.
Published: July 2007

Previous reports of 18 patients with Wegener's Granulomatosis treated with immunosuppressive and cytotoxic drugs are reviewed, and 4 new cases are reported. The prognosis in these patients is shown to be significantly better than that found in previous series where such drugs were not used
Niche differentiation and regeneration in the seasonally flooded Melaleuca forests of northern Australia
Authors: Franklin Donald C. , Brocklehurst Peter S. , Lynch Dominique , Bowman David M. J. S.
Published: July 2007

Gallery and floodplain forests in monsoonal northern Australia are mostly sclerophyllous and dominated by five closely related species of Melaleuca (Myrtaceae) amongst which niche differentiation is unclear. We present a floristic and environmental analysis of ‘the flooded forest’ using data from 340 plots distributed across 450 000 km2 of the Top End of the Northern Territory. Melaleuca argentea was confined to streams and occurred on sandier substrates, whereas M. cajuputi mostly occurred in the near-coastal lowlands on clay soils. The greater basal area of M. cajuputi suggests an association with productive sites. Melaleuca dealbata, M. viridiflora and M. leucadendra occurred on a wide range of soils. More deeply floodprone sites were occupied by M. argentea and M. leucadendra along streams and by M. leucadendra and M. cajuputi on floodplains and in swamps. A general deficiency but occasional abundance of Melaleuca seedlings suggests that regeneration is episodic. Seedlings were more frequent in recently burnt areas and especially where fires had been severe. We propose that Melaleuca forests occur where disturbance by fire and/or floodwater is too great for rain forest to persist, rendering them the wetland analogue to the eucalypts that dominate well-drained portions of the north Australian environment.
Pollination ecology of cardamom (Elettaria cardamomum) in the Western Ghats, India
Authors: Sinu Palatty Allesh , Shivanna K. R.
Published: July 2007

Heterogeneous agroforestry systems play an important role in maintaining animal pollinator diversity (Klein et al. 2003, Perfecto et al. 1996), most likely by extending floral resources in lean periods. An understanding of the mutualistic relationship between flower-visiting insects and crop species in such agroforestry systems (Kearns et al. 1998), particularly on the diversity of pollinator species, their spatio-temporal variations, foraging behaviour (Cunningham 2000, Greenleaf & Kremen 2006, Klein et al. 2003) and their pollination efficiency (Motten et al. 1981), is important as they are some of the crucial biological predictors of pollination success.
Vertical stratification in an acoustically communicating ensiferan assemblage of a tropical evergreen forest in southern India
Authors: Diwakar Swati , Balakrishnan Rohini
Published: July 2007

This study provides the first quantitative description of vertical stratification in calling heights of ensiferan species constituting most of the dry-season nocturnal acoustic community of an evergreen forest in Kudremukh National Park in south-west India. Calling heights of an average of 26 individuals of each of the 20 ensiferan species were measured and subjected to an analysis of variance to test for differences in mean calling height between species and a cluster analysis to check for the presence of discontinuous calling height layers. There were significant differences in mean calling heights between species. Calling heights of different gryllid and tettigoniid species ranged from the ground to the canopy. More gryllid than tettigoniid species occupied the ground and herb layer. Our study revealed vertical stratification of calling heights, with discrete layers corresponding to the canopy, understorey and the ground layer. These clusters emerged from the raw data of calling heights of individuals without a priori distinction of layers. We found no significant correlation between the calling heights of species and call features, including mean dominant frequency of narrow band calls, mean syllable rate and mean duty cycle.
Visual assessment of wilting as a measure of leaf water potential and seedling drought survival
Authors: Engelbrecht Bettina M. J. , Tyree Melvin T. , Kursar Thomas A.
Published: July 2007

Rainfall and soil moisture availability vary greatly both spatially and temporally. They are prime factors influencing species distribution patterns, diversity and habitat associations in a range of biomes, and limit primary productivity in many natural ecosystems, as well as in forestry and agricultural systems (Hawkins et al. 2003, Kozlowski & Pallardy 1997, Lieth 1975). Projections of drying trends, and increased frequency and intensity of drought events with climate and land-use changes (Hulme & Viner 1998, IPCC 2001) have fuelled an increased interest in the role of drought in determining the structure and function of natural and managed forest systems (Allen & Breshears 1998, Miles et al. 2004). Such projections accentuate the need to assess, understand and predict plant reactions to drought, as well as soil moisture variation at different scales.
On the evolution of consonant harmony: the case of secondary articulation agreement
Authors: Hansson Gunnar Ólafur
Published: July 2007

Consonant harmony involves long-distance featural assimilation, or agreement, of consonants across intervening segments. Current correspondence-based analyses of such sound patterns assume that they originate in the cognitive exigencies of articulatory planning, either synchronically, through the functional grounding of the constraints responsible, or diachronically, whereby processing factors incrementally shape the lexicon over time. This paper challenges the validity of this assumption as an all-purpose functional explanation for the full range of long-distance consonant agreement patterns by demonstrating that a variety of diachronic trajectories underlies their emergence and evolution. Focusing on the comparatively rare phenomenon ofsecondary articulation agreement, the evolutionary histories of three cases are examined: (labio)velarisation agreement in Pohnpeian (Oceanic), palatalisation agreement in Karaim (Turkic) and pharyngealisation agreement in Tsilhqot'in (Athabaskan). These histories provide explanations for a range of synchronic properties of the systems in question, some of which are problematic for restrictive typologies of consonant harmony.
Comparing methods for handling missing values in food-frequency questionnaires and proposing k nearest neighbours imputation: effects on dietary intake in the Norwegian Women and Cancer study (NOWAC)
Authors: Parr Christine L , Hjartåker Anette , Scheel Ida , Lund Eiliv , Laake Petter , Veierød Marit B
Published: July 2007

Objective

To investigate item non-response in a postal food-frequency questionnaire (FFQ), and to assess the effect of substituting/imputing missing values on dietary intake levels in the Norwegian Women and Cancer study (NOWAC). We have adapted and probably for the first time applied k nearest neighbours (KNN) imputation to FFQ data.

Design

Data from a recent reproducibility study were used. The FFQ was mailed twice (test–retest) about 3 months apart to the same subjects. Missing responses in the test FFQ were imputed using the null value (frequencies = null, amount = smallest), the sample mode, the sample median, KNN, and retest values.

Setting

A methodological substudy of NOWAC, a national population-based cohort.

Subjects

A random sample of 2000 women aged 46–75 years was drawn from the cohort in 2002 (response 75%). The imputation methods were compared for 1430 women who completed at least 50% of the test FFQ.

Results

We imputed 16% missing values in the overall test data matrix. Compared to null value imputation, the largest differences in estimated dietary intake were seen for KNN, and for food items with a high proportion of missing. Imputation with retest values increased total energy intake, indicating that not all missing values are caused by respondents failing to specify no consumption, and that null value imputation may lead to underestimation and misclassification.

Conclusion

Missing values in FFQs present a methodological challenge. We encourage the application and evaluation of newer imputation methods, including KNN, which may reduce imputation errors and give more accurate intake estimates.