bluuebunny/crossref_metadata_2025 huggingface dataset:
State-Space Approach to LQG Multivariable Predictive and Feedforward Optimal Control
Authors: Grimble M. J.
Published: March 2008

Two extensions of the LQG optimal control problem are presented which enable prediction and feedforward action to be introduced in a state equation framework. Predictive control is first considered using a discrete-time state-space system model. Future reference values are assumed to be known p-steps ahead and the controller has a two-degrees of freedom structure. The mechanism for introducing feedforward control and hence providing a third degree of freedom is also considered. Both prediction and feedforward action are simple to design and implement using the proposed state-space approach.
On the Generation of QFT Bounds for General Interval Plants
Authors: Zhao Yongdong , Jayasuriya Suhada
Published: March 2008

Considered in this paper is the question of synthesizing a fixed compensator for an interval plant so that (i) robust stability and (ii) robust disturbance rejection in the sense of Quantitative Feedback Theory (QFT) are attained. As expected, the problem reduces to one of loop shaping a nominal transfer function that avoids a set of frequency dependent forbidden regions while simultaneously stabilizing the nominal plant. It is shown that for the class of interval plants considered, the QFT boundaries (i.e., the magnitude restrictions on the nominal loop transfer function at each phase for a given frequency) can be explicitly computed by solving a number of simultaneous inequalities at each frequency. These results yield computationally efficient algorithms mainly because the need for the usual one dimensional search on the magnitude of the nominal loop transfer function has been completely removed.
Real Time Estimation of Engine Torque for the Detection of Engine Misfires
Authors: Connolly Francis T. , Rizzoni Giorgio
Published: March 2008

The need for improvements in the on-line estimation of engine performance variables is greater nowadays as a result of more stringent emission control legislation. There is also a concurrent requirement for improved on-board diagnostics to detect different types of malfunctions. For example, recent California Air Resources Board (CARB) regulations mandate continuous monitoring of misfires, a problem which, short of an expensive measurement of combustion pressure in each cylinder, is most directly approached by estimating individual cylinder torque. This paper describes the theory and experimental results of a method for the estimation of individual cylinder torque in automative engines, with the intent of satisfying the CARB misfire detection requirements. Estimation, control, and diagnostic functions associated with automotive engines involve near periodic processes, due to the nature of multi-cylinder engines. The model of the engine dynamics used in this study fully exploits the inherent periodicity of the combustion process in the crank angle domain in order to obtain a simple deconvolution method for the estimation of the mean torque produced by each cylinder during each stroke from a measurement of crankshaft angular velocity. The deconvolution is actually performed in the spatial frequency domain, recognizing that the combustion energy is concentrated at discrete spatial frequencies, which are harmonics of the frequency of rotation of the crankshaft. Thus, the resulting deconvolution algorithm is independent of engine speed, and reduces to an algebraic operation in the frequency domain. It is necessary to perform a Discrete Fourier Transform (DFT) on the measured angular velocity signal, sampled at fixed uniform crank angle intervals. The paper discusses the model used in the study, and the experimental validation of the algorithm, which has been implemented in real time using a portable computer and has been tested extensively on different production vehicles on a chassis dynamometer and on the road.
Real-Time Manipulation of a Hybrid Serial-and-Parallel-Driven Redundant Industrial Manipulator
Authors: Cheng H. H.
Published: March 2008

The real-time implementation of path planning, trajectory generation, and servo control for manipulation of the prototype UPSarm are presented in this paper. The prototype UPSarm, which is primarily designed for studying the feasibility of loading packages inside a trailer, is a ten degree-of-freedom hybrid serial-and-parallel-driven redundant robot manipulator. The direct, forward, inverse, and indirect kinematic solutions of the UPSarm using three coordinate spaces: actuator space, effective joint space, and world Cartesian coordinate space are derived for real-time path planning, trajectory generation, and control. The manipulation of the UPSarm is based upon a general-purpose path planner and trajectory generator. Provided with appropriate kinematics modules and sufficient computational power, this path planner and trajectory generator can be used for real-time motion control of any degree-of-freedom hybrid serial-and-parallel-driven electromechanical devices. A VMEbus-based distributed computing system has been implemented for real-time motion control of the UPSarm. A PID-based feedforward servo control scheme is used in our servo controller. The motion examples of the UPSarm programmed in our robot language will show the practical manipulation of hybrid serial-and-parallel-driven redundant kinematic chains.
Separated-Form Equations of Motion of Controlled Flexible Multibody Systems
Authors: Lieh Junghsen
Published: March 2008

This paper introduces a method leading to separated-form formulation of dynamic equations of multibody systems subject to control. The algorithm is derived from the virtual work principle and includes the moving base effects. The elastic members are treated as Euler-Bernoulli beams. Equations of motion are expanded using generalized coordinate partitioning and a Jacobian matrix expansion. The formulation of each physical term is separated, i.e., the inertia matrix, nonlinear coupling vector, generalized force vector and base motion-induced terms are established individually. The formulation is implemented on a workstation using MAPLE. Nonlinear and linearized equations with control are generated in FORTRAN format. The control design adopts second-order models directly. Several examples including a spin-up cantilever beam, an elastic vehicle with active suspensions and an elastic slider-crank mechanism are given. Numerical results for nonlinear and linear spin-up beam models are provided. Simulation for the active vehicle model using second-order control theory is presented.
Identification of Solar Collector Dynamics Using Physical Model-Based Approach
Authors: Huang B. J. , Wang S. B.
Published: March 2008

A system dynamics model of flat-plate solar collectors was derived and identified here. A nonlinear physical model was first derived from a two-node concept and energy conservation principle. The model was then approximated by the linear perturbation equations which were Laplace transformed and solved to lead to a distributed model in terms of the transfer functions. A model reduction was further employed to yield a linear time-invariant model with parameters as functions of steady-state operating conditions. The model parameters were identified by a dynamic test with step inputs at various operating conditions using frequency response analysis and model fitting in frequency domain. The identified parameters were then fitted to a function of steady-state mass flowrate mw. Thus, the model can describe the system dynamics behavior under various operating conditions through the identified parameters. The simulations using the model were shown to agree very well with the test results.
Identification of Structural System Parameters Using the Cascade-Correlation Neural Network
Authors: Smith H. Allison , Chase J. Geoffrey
Published: March 2008

The use of neural networks for structural system identification is receiving an increasing amount of attention through the research focused on structural control and intelligent systems. These systems require continuous monitoring and controlling of structural response; thus, on-line identification techniques are needed to provide real-time information about structural parameters. The Cascade-Correlation (Cascor) neural network is applied here to the structural system identification problem. The Cascor network utilizes a dynamic network architecture and a variable error threshold mechanism which facilitates training and can increase the network’s ability to generalize.
Sufficient Conditions for Monotonic Discrete Time Step Responses
Authors: de la Barra Bernardo Leo´n
Published: March 2008

Simple sufficient conditions for monotonic discrete time step responses are obtained and expressed in terms of the relative locations of discrete time zeros and poles. Frequency domain arguments are also introduced to complement these conditions. Simple examples are used to illustrate the main issues.
Coupling Effects in a Manipulator With Both a Flexible Link and Joint
Authors: Xi F. , Fenton R. G. , Tabarrok B.
Published: March 2008

The manipulator considered in this paper consists of a flexible link and a flexible joint. The coupling effect between link and joint deflections is investigated. The dynamic equations for the of manipulator are derived and analytical solutions are obtained. It is shown that the natural frequencies and mode shapes of a manipulator with both a flexible link and joint may be parametrized in terms of two ratios. One is the ratio of the moment of inertia of the link to that of the rotor and the other is the ratio of the link stiffness to the joint stiffness. Two special cases are discussed: (1) a manipulator with a relatively flexible link and a relatively rigid joint; and (2) a manipulator with a relatively flexible joint and a relatively rigid link.
Modeling, Experimentation and Simulation of a Brake Apply System
Authors: Khan Y. , Kulkarni P. , Youcef-Toumi K.
Published: March 2008

This study presents the development and validation of an analytical dynamic model of the brake apply system of a vehicle. The brake apply system includes the models for brake pedal, vacuum booster, master cylinder, and proportioning valves; the interactions with the wheel brake system, which comprises the front and rear foundation brakes, are included by modeling their compliances. Laboratory experiments are performed on a bench setup of the brake system and the experimental data is compared with the simulation results. The model is formulated such that the inputs are the pedal force applied by the driver, the vacuum supplied by the engine and the physical parameters of the brake components. Preliminary analysis shows that the simulation tracks the data quite closely throughout the regime of operation. Sensitivity studies are performed to show the effect of different friction parameters on the system performance.
Stability Robustness of LQ and LQG Active Suspensions
Authors: Ulsoy A. G. , Hrovat D. , Tseng T.
Published: March 2008

A two-degree-of-freedom quarter-car model is used as the basis for linear quadratic (LQ) and linear quadratic Gaussian (LQG) controller design for an active suspension. The LQ controller results in the best rms performance trade-offs (as defined by the performance index) between ride, handling and packaging requirements. In practice, however, all suspension states are not directly measured, and a Kalman filter can be introduced for state estimation to yield an LQG controller. This paper (i) quantifies the rms performance losses for LQG control as compared to LQ control, and (ii) compares the LQ and LQG active suspension designs from the point of view of stability robustness. The robustness of the LQ active suspensions is not necessarily good, and depends strongly on the design of a backup passive suspension in parallel with the active one. The robustness properties of the LQG active suspension controller are also investigated for several distinct measurement sets.
On Transfer Function Zeros of General Colocated Control Systems With Mechanical Flexibilities
Authors: Miu Denny K. , Yang Bingen
Published: March 2008

In our previous work, it was shown that for simple control systems with mechanical flexibilities such as spring-mass systems or uniform cross-section linear elastic beams, the complex conjugate transfer function zeros can be interpreted as the resonances of a sub-portion of the flexible structure with additional constraints imposed by the sensor and actuator. In this paper, the aforementioned intuitive physical observation is verified mathematically for general lumped and distributed parameter flexible control systems with colocated sensor/actuator.
Moving Sliding Surfaces for Fast Tracking Control of Second-Order Dynamical Systems
Authors: Choi Seung-Bok , Park Dong-Won
Published: March 2008

A new type of sliding surface for a variable structure control system is proposed to achieve fast and accurate path tracking in a class of nonlinear second-order multi-input dynamical systems. The surface is adaptable to arbitrary initial conditions, and movable towards a predetermined surface. The movement is executed in a stepwise manner according to the trajectory of representative points. We call it a moving sliding surface (MSS). Using the MSS favorable fast tracking is accomplished without increasing the magnitude of the discontinuous control gain. A two-degree-of-freedom robotic manipulator subjected to external disturbances is considered to demonstrate the efficacy of the proposed method.
Joint Stiffness Estimation Based on Force Sensor Measurements in Industrial Manipulators
Authors: Ferretti G. , Maffezzoni C. , Magnani G. , Rocco P.
Published: March 2008

The problem of estimating the stiffness constants of the joints in industrial manipulators is addressed in this paper. It is shown that the model of the robot constrained by a rigid environment yields a simple relationship between variations of the motor coordinates and the forces arising at the contact with the environment. By exploiting the measurements of the motor positions sensors and of a force sensor located at the end effector a method is proposed to simply compute good estimates of the stiffness constants. Experiments have been made on the industrial robot SMART and the results are given and discussed.
Deterministic Controllers for a Class of Mismatched Systems
Authors: Sandeep
Published: March 2008

In this paper a class of nonlinear uncertain dynamical systems, which do not satisfy the matching conditions, is considered. This class of mismatched systems is more general than one considered earlier. A sufficient condition, in terms of a critical mismatch threshold, is given, which ensures uniform boundedness and uniform ultimate boundedness. The theory is illustrated by an example of controlled aircraft take-off under windshear conditions.
Two-Dimensional Exact Model Matching With Application to Repetitive Control
Authors: Alter David M. , Tsao Tsu-Chin
Published: March 2008

This paper concerns matching a system with time-delayed feedback to a rational transfer function model and its application to repetitive controller design. Necessary and sufficient conditions on the order of the plant, reference model, and controller are obtained for the existence of causal and stabilizing exact model matching solutions. The results are applied to robust repetitive controller design, in which a delayed feedback is introduced in the repetitive controller for rejecting periodic disturbances while simultaneously achieving input-output model matching. Furthermore, the 2-D model matching method also renders computationally efficient solutions. Also addressed are some subtle points on the selection of a low-pass filter required for robust stability. Finally, the approach is experimentally applied for turning noncircular shapes.
Dynamic Modeling of Constrained Flexible Robot Arms for Controller Design
Authors: Hu F. L. , Ulsoy A. G.
Published: March 2008

The modeling for controller design of a constrained rigid-flexible robot arm is considered. The mathematical model is obtained as a set of nonlinear hybrid ordinary-partial differential equations and an algebraic constraint equation. Galerkin’s method is employed to discretize the partial differential equations. Because of the constrained environment of the robot arm, the choice of approximating functions in the spatial discretization is crucial for obtaining accurate simulation results from a low order model. Several candidate approximating functions are evaluated through convergence and accuracy studies. This work also investigates the effects of coupling between rigid- and flexible-body motion, and the effects of axial force (due to the contact force) on bending vibrations through axial shortening. It is shown that the use of inappropriate spatial approximating functions with a low order model can result in faulty predictions of the dynamic response, especially, the axial force effects due to the contact force.
A Numerical and Experimental Analysis of a Chain of Flexible Bodies
Authors: Giovagnoni Marco
Published: March 2008

A flexible multi-body dynamics approach is described. It uses an equivalent rigid link system from which are measured small displacements. The equations of motion are obtained by direct application of the principle of virtual work. Some terms in the virtual and real components have been neglected by virtue of the small displacement assumption. The use of sensitivity coefficients allows one to obtain a formulation which can be easily interfaced with any kinematic solution algorithm. It also enables one to check the correctness of the chosen equivalent rigid link system. The theory is then employed to reproduce numerically the experimental recordings obtained from a flexible linkage. Agreement between experimental and numerical data is good.
Biological Activities of Novel Gyrase Inhibitors of the Aminocoumarin Class
Authors: Anderle Christine , Stieger Martin , Burrell Matthew , Reinelt Stefan , Maxwell Anthony , Page Malcolm , Heide Lutz
Published: March 2008

Thirty-one aminocoumarin antibiotics derived from mutasynthesis experiments were investigated for their biological activities. Their inhibitory activities towardEscherichia coliDNA gyrase were determined in two different in vitro assays: an ATPase assay and a DNA supercoiling assay. The assays gave a similar rank order of the activities of the compounds tested, although the absolute 50% inhibitory concentrations (IC50s) obtained in each assay were different. To confirm that the compounds also acted as gyrase inhibitors in vivo, reporter gene assays were carried out withE. coliby usinggyrAandsulApromoter fusions with theluxCDABEoperon. A strong induction of both promoters was observed for those compounds that showed gyrase inhibitory activity in the biochemical assays. Compounds carrying analogs of the prenylated benzoyl moiety (ring A) of clorobiocin that were structurally very different showed high levels of activity both in the biochemical assay and in the reporter gene assay, indicating that the structure of this moiety can be varied considerably without a loss of affinity for bacterial gyrase. The experimentally determined IC50s were compared to the binding energies calculated in silico, which indicated that a shift of the pyrrole carboxylic acid moiety from the O-3″ to the O-2″ position of the deoxysugar moiety has a significant impact on the binding mode of the compounds. The aminocoumarin compounds were also investigated for their MICs against different bacterial pathogens. Several compounds showed high levels of activity against staphylococci, including a methicillin-resistantStaphylococcus aureusstrain. However, they showed only poor activities against gram-negative strains.
Detection of Methyltransferases Conferring High-Level Resistance to Aminoglycosides in Enterobacteriaceae from Europe, North America, and Latin America
Authors: Fritsche Thomas R. , Castanheira Mariana , Miller George H. , Jones Ronald N. , Armstrong Eliana S.
Published: March 2008

The alteration of ribosomal targets by recently described 16S rRNA methyltransferases confers resistance to most aminoglycosides, including arbekacin.
Enterobacteriaceae
and nonfermentative bacilli acquired through global surveillance programs were screened for the presence of these enzymes on the basis of phenotypes that were resistant to nine tested aminoglycosides. Subsequent molecular studies determined that 20 of 21 (95.2%) methyltransferase-positive isolates consisted of novel species records or geographic occurrences (North America [
armA
and
rmtB
], Latin America [
rmtD
], and Europe [
armA
];
rmtA
,
rmtC
, and
npmA
were not detected). The global emergence of high-level aminoglycoside resistance has become a rapidly changing event requiring careful monitoring.
Efficacy of Gamma Interferon and Specific Antibody for Treatment of Microsporidiosis Caused byEncephalitozoon cuniculiin SCID Mice
Authors: Salát Jiří , Jelínek Jiří , Chmelař Jindřich , Kopecký Jan
Published: March 2008

Microsporidia are eukaryotic, obligate, intracellular protists that are emerging pathogens in immunocompromised hosts, including AIDS patients and organ transplant recipients. The efficacy of gamma interferon (IFN-γ) for the treatment of microsporidiosis caused byEncephalitozoon cuniculiwas studied by means of adoptive transfer and IFN-γ administration in SCID mice. While the adoptive transfer of CD4+T cells from immunocompetent mice prolonged survival of SCID mice infected perorally withE. cuniculi, survival was not improved by adoptive transfer of CD4+T lymphocytes from IFN-γ-deficient mice. The protective effect of IFN-γ was confirmed in cytokine therapy experiments in which SCID mice receiving IFN-γ survived significantly longer than mice receiving mock injections. The administration of serum containing specific antibodies againstE. cuniculiwas found to prolong the survival of concurrently IFN-γ-treated SCID mice. The data presented in this study suggest that IFN-γ is potentially useful as a cytokine therapy for microsporidiosis, especially in CD4+T-cell-deficient patients.
Susceptibility Testing of Anidulafungin and Voriconazole Alone and in Combination against Conidia and Hyphae of
Aspergillus
spp. under Hypoxic Conditions
Authors: Perkhofer Susanne , Jost Daniel , Dierich Manfred P. , Lass-Flörl Cornelia
Published: March 2008

MICs and fractional inhibitory concentrations were evaluated for anidulafungin and voriconazole alone and in combination against conidia and hyphae under hypoxic (1% oxygen-5% CO
2
-94% nitrogen) conditions against 31
Aspergillus
isolates. Anidulafungin exhibited excellent activity against conidia and hyphae of
Aspergillus
spp. The visual reading of the MIC for anidulafungin was optimal under hypoxic conditions.
Identification of TbpA Residues Required for Transferrin-Iron Utilization by
Neisseria gonorrhoeae
Authors: Noto Jennifer M. , Cornelissen Cynthia Nau
Published: March 2008

Neisseria gonorrhoeae
requires iron for survival in the human host and therefore expresses high-affinity receptors for iron acquisition from host iron-binding proteins. The gonococcal transferrin-iron uptake system is composed of two transferrin binding proteins, TbpA and TbpB. TbpA is a TonB-dependent, outer membrane transporter critical for iron acquisition, while TbpB is a surface-exposed lipoprotein that increases the efficiency of iron uptake. The precise mechanism by which TbpA mediates iron acquisition has not been elucidated; however, the process is distinct from those of characterized siderophore transporters. Similar to these TonB-dependent transporters, TbpA is proposed to have two distinct domains, a β-barrel and a plug domain. We hypothesize that the TbpA plug coordinates iron and therefore potentially functions in multiple steps of transferrin-mediated iron acquisition. To test this hypothesis, we targeted a conserved motif within the TbpA plug domain and generated single, double, and triple alanine substitution mutants. Mutagenized TbpAs were expressed on the gonococcal cell surface and maintained wild-type transferrin binding affinity. Single alanine substitution mutants internalized iron at wild-type levels, while the double and triple mutants showed a significant decrease in iron uptake. Moreover, the triple alanine substitution mutant was unable to grow on transferrin as a sole iron source; however, expression of TbpB compensated for this defect. These data indicate that the conserved motif between residues 120 and 122 of the TbpA plug domain is critical for transferrin-iron utilization, suggesting that this region plays a role in iron acquisition that is shared by both TbpA and TbpB.
Glycogen and Maltose Utilization by
Escherichia coli
O157:H7 in the Mouse Intestine
Authors: Jones Shari A. , Jorgensen Mathias , Chowdhury Fatema Z. , Rodgers Rosalie , Hartline James , Leatham Mary P. , Struve Carsten , Krogfelt Karen A. , Cohen Paul S. , Conway Tyrrell
Published: March 2008

Mutant screens and transcriptome studies led us to consider whether the metabolism of glucose polymers, i.e., maltose, maltodextrin, and glycogen, is important for
Escherichia coli
colonization of the intestine. By using the streptomycin-treated mouse model, we found that catabolism of the disaccharide maltose provides a competitive advantage in vivo to pathogenic
E. coli
O157:H7 and commensal
E. coli
K-12, whereas degradation of exogenous forms of the more complex glucose polymer, maltodextrin, does not. The endogenous glucose polymer, glycogen, appears to play an important role in colonization, since mutants that are unable to synthesize or degrade glycogen have significant colonization defects. In support of the hypothesis that
E. coli
relies on internal carbon stores to maintain colonization during periods of famine, we found that by providing a constant supply of a readily metabolized sugar, i.e., gluconate, in the animal's drinking water, the competitive disadvantage of
E. coli
glycogen metabolism mutants is rescued. The results suggest that glycogen storage may be widespread in enteric bacteria because it is necessary for maintaining rapid growth in the intestine, where there is intense competition for resources and occasional famine. An important implication of this study is that the sugars used by
E. coli
are present in limited quantities in the intestine, making endogenous carbon stores valuable. Thus, there may be merit to combating enteric infections by using probiotics or prebiotics to manipulate the intestinal microbiota in such a way as to limit the availability of sugars preferred by
E. coli
O157:H7 and perhaps other pathogens.
Yersinia pestis caf1Variants and the Limits of Plague Vaccine Protection
Authors: Quenee Lauriane E. , Cornelius Claire A. , Ciletti Nancy A. , Elli Derek , Schneewind Olaf
Published: March 2008

Yersinia pestis, the highly virulent agent of plague, is a biological weapon. Strategies that prevent plague have been sought for centuries, and immunization with live, attenuated (nonpigmented) strains or subunit vaccines with F1 (Caf1) antigen is considered effective. We show here that immunization with live, attenuated strains generates plague-protective immunity and humoral immune responses against F1 pilus antigen and LcrV.Y. pestisvariants lackingcaf1(F1 pili) are not only fully virulent in animal models of bubonic and pneumonic plague but also break through immune responses generated with live, attenuated strains or F1 subunit vaccines. In contrast, immunization with purified LcrV, a protein at the tip of type III needles, generates protective immunity against the wild-type and the fully virulentcaf1mutant strain, in agreement with the notion that LcrV can elicit vaccine protection against both types of virulent plague strains.
Genetic Evidence for an Alternative Citrate-Dependent Biofilm Formation Pathway in
Staphylococcus aureus
That Is Dependent on Fibronectin Binding Proteins and the GraRS Two-Component Regulatory System
Authors: Shanks Robert M. Q. , Meehl Michael A. , Brothers Kimberly M. , Martinez Raquel M. , Donegan Niles P. , Graber Martha L. , Cheung Ambrose L. , O'Toole George A.
Published: March 2008

We reported previously that low concentrations of sodium citrate strongly promote biofilm formation by
Staphylococcus aureus
laboratory strains and clinical isolates. Here, we show that citrate promotes biofilm formation via stimulating both cell-to-surface and cell-to-cell interactions. Citrate-stimulated biofilm formation is independent of the
ica
locus, and in fact, citrate represses polysaccharide adhesin production. We show that fibronectin binding proteins FnbA and FnbB and the global regulator SarA, which positively regulates
fnbA
and
fnbB
gene expression, are required for citrate's positive effects on biofilm formation, and citrate also stimulates
fnbA
and
fnbB
gene expression. Biofilm formation is also stimulated by several other tricarboxylic acid (TCA) cycle intermediates in an FnbA-dependent fashion. While aconitase contributes to biofilm formation in the absence of TCA cycle intermediates, it is not required for biofilm stimulation by these compounds. Furthermore, the GraRS two-component regulator and the GraRS-regulated efflux pump VraFG, identified for their roles in intermediate vancomycin resistance, are required for citrate-stimulated cell-to-cell interactions, but the GraRS regulatory system does not impact the expression of the
fnbA
and
fnbB
genes. Our data suggest that distinct genetic factors are required for the early steps in citrate-stimulated biofilm formation. Given the role of FnbA/FnbB and SarA in virulence in vivo and the lack of a role for
ica
-mediated biofilm formation in
S. aureus
catheter models of infection, we propose that the citrate-stimulated biofilm formation pathway may represent a clinically relevant pathway for the formation of these bacterial communities on medical implants.
Wall Teichoic Acid Deficiency inStaphylococcus aureusConfers Selective Resistance to Mammalian Group IIA Phospholipase A2and Human β-Defensin 3
Authors: Koprivnjak Tomaz , Weidenmaier Christopher , Peschel Andreas , Weiss Jerrold P.
Published: March 2008

Wall teichoic acids (WTAs) and membrane lipoteichoic acids (LTAs) are the major polyanionic polymers in the envelope ofStaphylococcus aureus. WTAs inS. aureusplay an important role in bacteriophage attachment and bacterial adherence to certain host cells, suggesting that WTAs are exposed on the cell surface and could also provide necessary binding sites for cationic antimicrobial peptides and proteins (CAMPs). Highly cationic mammalian group IIA phospholipase A2(gIIA PLA2) killsS. aureusat nanomolar concentrations by an action(s) that depends on initial electrostatic interactions, cell wall penetration, membrane phospholipid (PL) degradation, and activation of autolysins. AtagOmutant ofS. aureusthat lacks WTA is up to 100-fold more resistant to PL degradation and killing by gIIA PLA2and CAMP human β-defensin 3 (HBD-3) but has the sensitivity of the wild type (wt) to other CAMPs, such as Magainin II amide, hNP1-3, LL-37, and lactoferrin. In contrast, there is little or no difference in either gIIA PLA2activity toward cell wall-depleted protoplasts of the wt andtagOstrains ofS. aureusor in binding of gIIA PLA2to wt andtagOstrains. Scanning and transmission electron microscopy reveal increased surface protrusions in theS. aureus tagOmutant that might account for reduced activity of bound gIIA PLA2and HBD-3 toward thetagOmutant. In summary, the absence of WTA inS. aureuscauses a selective increase in bacterial resistance to gIIA PLA2and HBD-3, the former apparently by reducing access and/or activity of bound antibacterial enzyme to the bacterial membrane.
Lipooligosaccharides Containing Phosphorylcholine Delay Pulmonary Clearance of NontypeableHaemophilus influenzae
Authors: Pang Bing , Winn Dana , Johnson Ryan , Hong Wenzhou , West-Barnette Shayla , Kock Nancy , Swords W. Edward
Published: March 2008

NontypeableHaemophilus influenzae(NTHi) causes pulmonary infections in patients with chronic obstructive pulmonary disease and other mucociliary clearance defects. Like many bacteria inhabiting mucosal surfaces, NTHi produces lipooligosaccharide (LOS) endotoxins that lack the O side chain. Persistent NTHi populations express a discrete subset of LOS glycoforms, including those containing phosphorylcholine (PCho). In this study, we compared two NTHi strains with isogenic mutants lacking PCho for clearance from mice following pulmonary infection. Consistent with data from other model systems, populations of the strains NTHi 2019 and NTHi 86-028NP recovered from mouse lung contained an increased proportion of PCho+variants compared to that in the inocula. PCho−mutants were more rapidly cleared. Serial passage of NTHi increased both PCho content and bacterial resistance to clearance, and no such increases were observed for PCho−mutants. Increased PCho content was also observed in NTHi populations within non-endotoxin-responsive C3H/HeJ and Toll-like receptor 4 null (TLR4−/−) mice, albeit at later times postinfection. Changes in bacterial subpopulations and clearance were unaffected in TLR2−/−mice compared to the subpopulations in and clearance from mice of the parental strain. The clearance of PCho−mutants occurred at earlier time points in both strain backgrounds and in all types of mice. Comparison of bacterial populations in lung tissue cryosections by immunofluorescent staining showed sparse bacteria within the air spaces of C57BL/6 mice and large bacterial aggregates within the lungs of MyD88−/−mice. These results indicate that PCho promotes bacterial resistance to pulmonary clearance early in infection in a manner that is at least partially independent of the TLR4 pathway.
Measuring change in psychosocial working conditions: methodological issues to consider when data are collected at baseline and one follow-up time point
Authors: Smith P , Beaton D
Published: March 2008

If policy makers and employers are to take health issues into account when making decisions that will impact on work practices and work environments, they will need accurate information concerning the impact change in psychosocial working conditions has on health status. Although research is increasing in this area, a variety of different methods have been used to define when change in work conditions has occurred. The present paper considers various issues related to the accurate assessment of change in psychosocial working conditions, focusing on research designs that involve the collection of data at baseline and a single follow-up time point. The aim is to inform investigators about these methodological issues so they can be considered in the design of studies, the analysis of data and the interpretation of research findings.
Établissement du profil de l’activité physique et de l’inactivité : la prochaine générationCet article est tiré d’un supplément intitulé Advancing physical activity measurement and guidelines in Canada: a scientific review and evidence-based foundation for the future of Canadian physical activity guidelines (Favoriser les lignes directrices et la mesure de l’activité physique au Canada: examen scientifique et justification selon les données probantes pour l’avenir des lignes directrices de l’activité physique canadienne) publié par Physiologie appliquée, nutrition et métabolisme et la Revue canadienne de santé publique. On peut aussi mentionner Appl. Physiol. Nutr. Metab. 32 (Suppl. 2F) ou Can. J. Public Health 98 (Suppl. 2).
Authors: Esliger Dale W. , Tremblay Mark S.
Published: March 2008

L’évaluation précise de la quantité d’activité physique pratiquée de façon régulière constitue une donnée fondamentale dans l’étude de la relation entre l’activité physique et la santé. Cependant, plusieurs techniques de mesure de l’activité physique ne donnent que des résultats valables pour une seule journée comme, par exemple, la dépense d’énergie réalisée d’après une auto-évaluation par questionnaire, le nombre de pas fait d’après un podomètre, l’intensité d’activité physique mesurée au moyen d’un accéléromètre comptant le temps à faire des exercices d’intensité modérée à vigoureuse. On peut maintenant utiliser les techniques de monitorage qui informent davantage sur les comportements actifs et sédentaires pour approfondir l’étude de la relation entre la santé et la fréquence, l’intensité et la durée des mouvements accomplis. Cet article présente comment un monitorage objectif, avec une attention particulière portée à l’accélérométrie, peut dresser un bilan d’activité / d’inactivité. Au moyen de données objectives prélevées dans la littérature, on présente un bilan kinésique détaillé et des exemples d’étude de cas incorporant des données et leur interprétation. La quantité d’informations recueillies dans ce profil complet offre de nouvelles avenues de surveillance et d’études scientifiques pouvant déboucher sur de nouvelles directives en matière de pratique de l’activité physique. Nous présentons les résultats de diverses façons pour démontrer les dangers d’une mauvaise interprétation des données quand on évalue une population d’après son taux de conformité aux directives contenues dans le Guide d’activité physique canadien. Nous énonçons des recommandations en matière de profil kinésique / akinésique et nous proposons quelques pistes de recherche.
Le vieillissement et l’activité physique : données sur lesquelles fonder des recommandations relatives à l’exercice à l’intention des adultes âgésCet article est tiré d’un supplément intitulé Advancing physical activity measurement and guidelines in Canada: a scientific review and evidence-based foundation for the future of Canadian physical activity guidelines (Favoriser les lignes directrices et la mesure de l’activité physique au Canada: examen scientifique et justification selon les données probantes pour l’avenir des lignes directrices de l’activité physique canadienne) publié par Physiologie appliquée, nutrition et métabolisme et la Revue canadienne de santé publique. On peut aussi mentionner Appl. Physiol. Nutr. Metab. 32 (Suppl. 2F) ou Can. J. Public Health 98 (Suppl. 2).
Authors: Paterson Donald H. , Jones Gareth R. , Rice Charles L.
Published: March 2008

De nombreuses études épidémiologiques confirment les bienfaits procurés par l’activité physique en ce qui concerne la diminution du risque de maladie associée à l’âge et de la mortalité quelle qu’en soit la cause. L’analyse de la littérature scientifique centrée sur les caractéristiques principales (intensité, type, quantité) montre que la quantité nécessaire d’activité physique est celle qui améliore la condition cardiorespiratoire, la force musculaire, la puissance et, indirectement, l’équilibre. L’appauvrissement de ces fonctions avec l’âge entraîne des limitations physiques qui conditionnent les activités fonctionnelles journalières. En revanche, un programme d’activité physique peut atténuer ces pertes, évitant ainsi aux personnes âgées (plus de 65 ans) de traverser le seuil de l’incapacité physique. Les études transversales et longitudinales révèlent un lien entre la condition cardiorespiratoire et la capacité fonctionnelle et l’autonomie ; la force musculaire et par surcroît, la puissance musculaire, permettent d’accomplir plus efficacement les activités de tous les jours ; l’équilibre dynamique en combinaison avec la puissance musculaire forment un ensemble de prévention contre les chutes. D’après les études sur les programmes d’intervention, les personnes âgées peuvent améliorer leurs capacités fonctionnelles car elles possèdent la capacité d’adaptation à l’entraînement physique. Les quelques études qui ont analysé les quantités minimale et optimale d’activité physique indiquent qu’il faut faire des exercices dans les plages d’intensité modérée à vigoureuse si on veut atteindre et préserver les gains résultant de la pratique régulière. Par conséquent, on devrait prescrire des activités physiques en spécifiant le type d’activité qui améliorera les variables organiques associées au maintien de la capacité fonctionnelle et de l’autonomie et, de ce fait, on repoussera la maladie et la mort. Une bonne recommandation concernant l’exercice physique chez les personnes âgées devrait inclure des activités cardiorespiratoires modérément vigoureuses (la marche rapide), un entraînement à la force et à la puissance pour la préservation de la masse musculaire et de la capacité de travail de groupes musculaires choisis et des exercices d’équilibre et d’étirement au besoin.
L’activité physique des enfants d’âge préscolaire — somme et méthode?Cet article est tiré d’un supplément intituléAdvancing physical activity measurement and guidelines in Canada: a scientific review and evidence-based foundation for the future of Canadian physical activity guidelines(Favoriser les lignes directrices et la mesure de l’activité physique au Canada: examen scientifique et justification selon les données probantes pour l’avenir des lignes directrices de l’activité physique canadienne) publié parPhysiologie appliquée, nutrition et métabolismeet laRevue canadienne de santé publique. On peut aussi mentionner Appl. Physiol. Nutr. Metab. 32 (Suppl. 2F) ou Can. J. Public Health 98 (Suppl. 2).
Authors: Timmons Brian W. , Naylor Patti-Jean , Pfeiffer Karin A.
Published: March 2008

Alarming trends in childhood obesity even among preschool children have re-focused attention on the importance of physical activity in this age group. With this increased attention comes the need to identify the amount and type of physical activity appropriate for optimal development of preschool children. The purpose of this paper is to provide the scientific evidence to support a link between physical activity and biological and psychosocial development during early childhood (ages 2–5 years). To do so, we summarize pertinent literature informing the nature of the physical activity required to promote healthy physical, cognitive, emotional, and social development during these early years. A particular focus is on the interaction between physical activity and motor skill acquisition. Special emphasis is also placed on the nature of physical activity that promotes healthy weight gain during this period of childhood. The paper also discusses the strongest determinants of physical activity in preschool-age children, including the role of the child’s environment (e.g., family, child-care, and socio-economic status). We provide recommendations for physical activity based on the best available evidence, and identify future research needs.
Les guides d’activité physique du Canada : contexte, processus et élaborationCet article est tiré d’un supplément intitulé Advancing physical activity measurement and guidelines in Canada: a scientific review and evidence-based foundation for the future of Canadian physical activity guidelines (Favoriser les lignes directrices et la mesure de l’activité physique au Canada: examen scientifique et justification selon les données probantes pour l’avenir des lignes directrices de l’activité physique canadienne) publié par Physiologie appliquée, nutrition et métabolisme et la Revue canadienne de santé publique. On peut aussi mentionner Appl. Physiol. Nutr. Metab. 32 (Suppl. 2F) ou Can. J. Public Health 98 (Suppl. 2).
Authors: Sharratt Michael T. , Hearst William E.
Published: March 2008

Cet article à caractère historique répertorie dans le temps les principales phases de l’élaboration des guides d’activité physique canadiens à l’intention des enfants, des adolescents, des adultes et des personnes âgées. Cet article trace les grandes lignes du processus et des étapes franchies, y compris sur le plan de l’information (où cela s’applique), en lien avec les partenaires nationaux, l’administration du projet, les communications de Santé Canada, le développement du produit, les appuis, la distribution et la mise en œuvre, les activités collatérales, les relations avec les médias et les modalités d’évaluation. Nous présentons aussi l’essentiel des études scientifiques qui sous-tendent les directives contenues dans les guides. De plus, nous exposons les divers projets d’évaluation des guides d’activité physique canadiens et leurs résultats, notamment en ce qui concerne les études scientifiques menées à propos des guides à l’intention des enfants et des jeunes (et les ressources qui accompagnent les guides).
EFFECT OF EUROPIUM DOPING ON ELECTRICAL PROPERTIES OF PZT FILMS
Authors: SHAO CHUNYU , WANG JING , DONG WEIJIE , CUI YAN , JI MIN
Published: March 2008

Samples of lead zirconate titanate Pb ( Zr 0.53 Ti 0.47) O 3 with europium ( Eu ) doping concentration of 0, 0.5, 1.5, 3 mol% (PEZT) were fabricated by sol–gel method. XRD spectra showed that the introduction of Eu into PZT favored the growth of (100) orientation. With 3% Eu content, the preferential orientation of the film converted from (111) to (100) orientation. The Eu -doped PZT films exhibited lower leakage current less than 10-9 A/cm2 and the behavior of leakage current was discussed in terms of defect chemistry theorem. When Eu content was 1.5%, the remanent polarization (P r ) increased to 28 μ C/cm2 which was much higher than that of undoped PZT film.
ENHANCED DIELECTRIC CHARACTERISTICS OF MANGANESE-DOPED BZT THIN FILMS
Authors: ZHU J. , JIE W. J. , WEI X. H. , QIN W. F. , ZHANG Y. , LI Y. R.
Published: March 2008

Ba ( Zr 0.2 Ti 0.8) O 3 (BZT) and 2 mol% Mn additional doped BZT ( Mn -BZT) thin films were deposited by pulsed laser deposition technique under the same growth conditions on LaAlO 3 substrates with the bottom electrodes of LaNiO 3. The microstructure of the films was characterized by X-ray diffraction (XRD) in the mode of θ–2θ scan and Φ-scan. The results indicated that BZT film was (001)-oriented_with an in-plane relationship of BZT[100]//LNO[100]//LAO[100]. The Mn -BZT film exhibited higher dielectric constant of 225 at zero electric field, larger dielectric tunability of 59.4%, and lower dielectric loss of 1.8% under an applied electric field of 720 kV/cm. The figure of merit for BZT thin film increased from 19.8 to 33 by Mn doping. The enhanced dielectric behavior by Mn doping could be mainly attributed to the decrease of oxygen vacancies and the reorientation of the dipolar defect complex of [Formula: see text].
DENSIFICATION AND FERROELECTRIC PROPERTIES OF PZT(60/40) THICK FILMS FABRICATED BY SCREEN-PRINTING METHOD
Authors: LEE SUNG-GAP , NOH HYUN-JI , LEE YOUNG-HIE
Published: March 2008

Ferroelectric PbZr 0.6 Ti 0.4 O 3 (PZT) thick films were fabricated using a combination of screen-printing method and PZT precursor sol coating process (M. Koch, N. Harris, R. Maas, A. G. R. Evans, N. M. White and A. Brunnschweiler, Meas. Sci. Technol.8 (1997) 49; Y. S. Yoon, J. Korean. Phys. Soc.47 (2005) 321). Structural and electrical properties of the PZT thick films with the treatment of sol coating were investigated. The porosity decreased and the densification was enhanced with increasing the number of sol coatings. All PZT thick films showed the typical X-ray diffraction patterns of a perovskite polycrystalline structure. The thickness of all thick films was approximately 60–61 μm. The relative dielectric constant increased and dielectric loss decreased with increasing the number of sol coatings, and the values of the six-layer PZT-6 film were 167.8, 0.78% at 1 kHz, respectively. The remanent polarization and coercive field of the 6-coated PZT-6 thick films were 14.1 μC/cm2 and 20.3 kV/cm, respectively.
OXIDATION OF THE TiAlLaN COATING BETWEEN 600°C AND 800°C IN AIR
Authors: NGUYEN THUAN DINH , LEE D. B.
Published: March 2008

The oxidation of Ti 19 Al 18 La 4 N 57 coating was studied at 600°C, 700°C, and 800°C for up to 30 h in air. The coating consisted of fine Ti 3 Al 3 N 2 polycrystals. The oxides formed were an amorphous mixture of Al 2 O 3, TiO 2, and La 2 O 3. During oxidation, nitrogen diffused out from the coating. The addition of 4 at.% La to the TiAlN coating deteriorated the soundness of the oxide film formed.