bluuebunny/crossref_metadata_2025 huggingface dataset:
Main flux‐saturation modelling ind‐qaxis models of induction machines using mixed current‐flux state‐space models
Authors: Levi E. , Krzeminski Z.
Published: July 2010

Main flux saturation in induction machines is most frequently modelled by selecting either stator and rotor d‐q axis currents or stator and rotor d‐q axis flux linkages as state‐space variables. This paper deals with so‐called mixed current‐flux state‐space models where either stator or rotor current space phasor is selected as one state‐space variable. The other state‐space variable is one of the three flux‐linkage space phasors in the machine (stator, magnetizing or rotor), so that six different state‐space models are encompassed. A generalised derivation procedure for all the six models is at first presented. Models are further given in developed form. It is shown that cross‐saturation effect is explicitly present in all the models. Derivation procedure and the models are verified by simulation and experimental investigation of induction generator self‐excitation.
Mathematical foundations of the instantaneous power concepts: A geometrical approach
Authors: Willems J. L.
Published: July 2010

In this paper a mathematical formalism, based on a geometrical approach, is proposed for defining the concepts of instantaneous active and instantaneous reactive power. Use is made of the dot product and the cross product for three‐dimensional vectors. The relationship with the analysis proposed by Akagi et al. and by Ferrero and co‐authors is discussed in detail. In particular it is shown that the proposed formalism is well suited to deal with three‐phase currents and voltages with zero‐sequence components.
Dynamic on‐line measurement of equivalent parameters of three‐phase systems for harmonic frequencies
Authors: Czarnecki L. S. , Staroszczyk Z.
Published: July 2010

A method of an on‐line measurement of equivalent parameters for harmonic frequencies of a three‐phase distribution system with harmonic generating loads is discussed in the paper. The impedances of the supply and the load, the complex RMS (CRMS) values of the load generated current harmonics, and the CRMS values of the distribution voltage harmonics are the subject of the measurement. It is shown that the on‐line measurement of these parameters requires that the line voltages and currents are measured at least in three different states of the system. These states of the tested system are changed by disturbing the system with a current harmonics generating device, built in a form of a fast thyristor switch. The method is illustrated with measurements in a physical system.
Criteria for the definition of the electric power quality and its measurement systems
Authors: Tugulea A.
Published: July 2010

An attempt to define the quality of physical and technical processes in general and of electric energy in particular is given, by considering the two main meanings of the quality: a set of properties and characteristic, a degree of excellence. It is emphasized the main role of the conservative parameters of quality. A Data Aquisi‐Hon System (DAS) for the monitoring of electric power quality is proposed and some results of measurements are given.
Some possible new applications of a partial‐discharge (PD) model and its relation to PD‐detection sensitivity
Authors: Danikas M. G.
Published: July 2010

In this paper some possibilities of further applications of a known “Streamer Partial‐Discharge Model” are proposed. These possibilities refer to the relation between the observed partial‐discharge (PD) magnitude and the applied field to the insulation. Furthermore, the model is a useful tool to investigate the sensitivity of a PD detector and also to compare the sensitivities between various PD detectors.
Time‐varying loads in electric power systems: Power input, equivalent circuit elements, and disturbances
Authors: Knoop M. , Köhle S.
Published: July 2010

Time‐varying electric loads, fluctuating around their nominal point, cause fluctuations also of current and power. The mean phasors of current and complex power differ from their nominal values, which results in a deflection of mean power input. A transformation to a time‐invariant equivalent circuit is introduced representing the mean values of voltage, current and power. The variances on the other hand contribute equations for a second phenomenon of fluctuating loads: the generation of disturbances in the power supply system. Results for both phenomena are derived for single‐phase loads, validated by Monte‐Carlo simulations, and generalized to three important kinds of three‐phase loads. Measured data from an electric arc furnace illustrate the application of ideas.
A chemical approach to the dielectric aging of fibre‐reinforced polymer (frp) insulators
Authors: Schrijver C. , Herden A. , Kärner H. C.
Published: July 2010

A time‐based model for the water‐influenced dielectric aging of FRP is presented, using chemical mechanisms to explain the measured increase of the loss tangent and the dielectric constant as well as the interphase orientation of the electrical breakdown channel in FRP insulators. Although this hypothesis is founded on artificial and accelerated aging of FRP specimens, it is also representative for real outdoor conditions. The model consists of three phases: I. water penetration by anomalous diffusion, leading to a weak increase of the dielectric parameters, 2. hydration of generated metal ions, causing a slight decrease of the dielectric constant and a strong increase of both, the loss tangent and the interphase conductivity and 3. a loss of adhesion, resulting in a strong increase of both, the dielectric parameters and the local electrical conductivity.
Enhanced selectivity and fault detection for distance protection in meshed grids by evaluating local 50‐hz‐phasors
Authors: Zettler K.‐R.
Published: July 2010

Due to different operating conditions distance protection units measure varying short‐circuit impedances (impedance uncertainty) and with that varying fault locations for one and the same short circuit. Therefore, it is necessary to reduce the reach of the respective time zones to avoid unwanted relay operation. This, however, may lead to an undesirable long fault clearance time. For the first time zone an optimal uncertainty minimizing strategy is presented based on pre‐fault power measured at the relay. For back‐up protection a method is proposed that minimizes the impedance uncertainty with the help of symmetrical components. As a result of meshed grids, the problem is often to detect short circuits in higher time zones on the whole. To cope with that problem a simple method is discussed, which allows an optimal distinction between load and fault states.
Accident control and stability of a pv induction motor pump set
Authors: Khashab H. El , Motaleb M. S. A. El
Published: July 2010

This paper presents a proposed algorithm for controlling an induction motor pump set powered from photovoltaic (PV) generator through a current source inverter. In particular, problems related to the efficiency of induction motors have received much attention due to their wide applications. An improved constant flux control system is used to optimize the motor efficiency by reducing the air‐gap flux. From an other interesting point of view, the reduced air‐gap flux may result in undesirable dynamic responses. In order to overcome this drawback, an accident stability region is designed using the eigenvalues‐zero pattern with the necessary linearization procedures.
Rotor‐field orientation with optimal torque‐control strategy for current‐fed induction‐machine system
Authors: El‐Sayed I. F.
Published: July 2010

Field orientation provides the possibility to control torque and flux of the induction machine independently. However, the widely used control strategy for field orientation is based on constant rotor flux. This strategy does not utilize all advantages by using field‐orientation method. This paper reveals a degree of freedom for controlling an induction machine, by controlling both field‐ and torque components. It presents a control strategy based on varying the flux level to provide optimum torque operation irrespective of speed ranges. The freedom for controlling both field‐ and torque components of the stator winding currents can make the inverter induction motor drive superior to DC drives, where proper resolving for the stator current components can provide maximum electromagnetic torque per ampere, optimal efficiency and higher short duty system capability. In this paper, the rotor‐field oriented saturated model of the induction machine is presented. The analysis of the electro‐magnetic torque, in terms of stator current components, is used to find the optimal resolving ratio for maximum torque. This optimal ratio depends on the machine parameters and the saturation level. Investigation and comparison for widely used and the proposed control strategies are given for different cases, namely: neglecting saturation effect case, then taking saturation into account for low‐ (0.75 kW) and high power rating (90 kW) machines. Also, the proposed optimal control strategy and the microprocessor implementation method are presented.
Sensor‐less, neuronal‐network‐based cage defect diagnosis for induction machines
Authors: Blattner J. , Gutt H.‐J.
Published: July 2010

This paper presents a PC‐based diagnosis system for cage defects in squirrel cage induction motors. Second‐order effects, like field and voltage harmonics, core currents and torque ripple caused current sidebands are integrated in a novel machine model for cage defects. In addition, the harmonic analysis display a way how the machine speed can be calculated out of the current spectrum. The experimental test of the diagnosis system reveals not only the ability to diagnose a defect cage, but also to distinguish different kind of defects.
Model to describe the chemical ageing behaviour of electrical busbar joints
Authors: Bergmann R. , Löbl H. , Böhme H. , Großmann S.
Published: July 2010

Electrical joints are subjected to an ageing process which can endanger the reliability of electrical power transmission systems. A mathematical model is presented with the help of which the ageing behaviour of electrical joints can be estimated depending on the conductor material, the construction of the joint, the assembly technology and the loading construction. The model is based on theoretical reflections as well as practical investigations on busbar joints for more than 16 years.
Prediction of the steady‐state performance of the switched reluctance motor using quadratic BIEM‐FEM field solutions in the linear model
Authors: Omekanda A. , Broche C. , Crappe M. , Baland R.
Published: July 2010

Prediction of the steady‐state performance of a switched reluctance motor (SRM) becomes complicated because of the complex influences between the motor parameters and excitation current. Accurate calculation of the electromagnetic quantities required for an SRM steady‐state prediction is not easy because these parameters are affected by intense saturation of the corners of partially overlapping stator and rotor poles. This paper presents a quadratic boundary‐integral equation (BIE) finite‐element (FE) method that has been proved accurate for the calculation of the motor parameters. The linear model of an SRM based on a trapezoidal evolution of a phase inductance versus rotor position for a constant excitation current is exploited. The instantaneous phase current and the average torque in the SRM angle‐controlled modes of operation are computed using the results of the BIE‐FE method with the analytical solution of the electrical differential equation describing the SRM drive. The prediction of the total average torque in a steady‐state angle‐controlled mode of a SRM drive operation agrees favourably with experimental results.
A method for probabilistic harmonic load‐flow analysis in power systems
Authors: Lehtonen M.
Published: July 2010

A new probabilistic method is presented for the harmonic load‐flow analysis in electrical power systems. In the method, the network is modelled using the bus impedance matrix at each harmonic order. The load flow is solved by a current injection method. For harmonic sources, the amplitude variation and the phase angle variation are taken into account. For the summation of the harmonics originating from different sources, a probability density function, derived from the jointly normal distribution is used. As a final result, statistical estimates are obtained for the node voltages and branch currents of each harmonic frequency considered.
Fault distance estimation and fault type determination using least error squares method
Authors: Terzija V. V. , Djuric M. B. , Radojevic Z. M.
Published: July 2010

In order to avoid autoreclosure onto a permanent fault, a new numerical algorithm for fault type determination is presented. It estimates the fault distance, as well, and can be utilized in the field of distance protection. The new approach, mathematical model and the solution for the earthless faults is given. For the purpose of unknown fault distance and arc voltage amplitude estimation, the Least Error Squares Method is used. The new algorithm is tested through numerous computer simulations and in the laboratory environment.
Principal of the direct determination of the temperature‐dependant rotor and stator resistances of an induction motor
Authors: Amin B.
Published: July 2010

In the presented paper, a direct method for evaluating the temperature‐dependant values of the rotor and stator resistances is presented. The method is based on the evaluation of the instant powers dissipated within these two resistances using the equation of the power balance. Moreover, the way of evaluating accurately the instant values of the rotor current is indicated. Finally, the average temperature of the windings and the values of the resistances are calculated.
Calculation of current flow in grounding systems of substations and of HV line towers, in line shield wires and cable sheaths during earth faults
Authors: Gatta F. M. , Iliceto F.
Published: July 2010

The paper presents a method and a numerical calculation program of the repartition of the earth‐fault currents in the grounding systems of substations and of the HV line towers, as well as of the currents which flow in the shield wires of the overhead lines and/or in the sheaths and armourings of underground cables. The program may be applied also to very extendednetworks for single‐phase‐to‐ground (1‐ϕ‐to‐Gr) andphase‐to‐phase‐to‐ground (ϕ‐ϕ‐to‐Gr) faults at any point. The program is based on the simulation of the earth resistances of the HV line towers by means of a transversal conductance uniformly distributed between the shield wires and earth, and which is assumed to be variable from stretch to stretch according to soil resistivity. Models are derived which are aimed at simulating the single and double‐circuit overhead lines provided with shield wires, as well as the underground cables. These models consist in a single three‐pole or four‐pole equivalent circuit. The validity of the program is verified by comparison with the calculations carried out by the Electromagnetic Transients Program (EMTP). Mention is made of a study carried out for the Turkish 420/150‐k V network. Some measures presented are aimed at reducing the currents which flow in the shield wires of the lines outgoing from the power plants/substations following faults nearby.
Permanent‐magnet synchronous drive with wide field‐weakening range
Authors: Binder A. , Greubel K. , Piepenbreier B. , Tölle H.‐J.
Published: July 2010

High‐speed small‐ to medium‐power inverter‐fed AC drives with wide field‐weakening range are realized nowadays preferably as induction motor drives. Nevertheless, in the field‐weakening range the utilization of the inverter is rather poor due to the decreasing power factor with increasing speed. In this paper it is shown both by theory and experiment that with permanent‐magnet synchronous machines ‐ in spite of the fixed rotor flux ‐field‐weakening is possible with large ratios of maximum/base speed. This is achieved by an additional negative stator current d‐component. The inverter rating for the same motor output power may be smaller by about 30 % to 40 %, as compared with the induction motor drive.
Digital simulation of reliability of contacts used in AC electromagnetic contactors
Authors: Wróblewski Z.
Published: July 2010

In the paper both general and simplified reliability models of contacts used in electromagnetic power contactors are presented. The models are based on digital simulation of contact‐wearing processes. The general model can be used for the estimation of influence of material and design parameters as well as operating conditions on contact durability while the simplified one is meant for forecasting new contact durability by means of simplified quality tests carried out on samples of brand new contactors.
Fast dynamic stability analysis of a power system using artificial neural networks
Authors: Kukolj D. , Popovic D. , Kulic F. , Gorecan Z.
Published: July 2010

This paper deals with the methodology of analysing the dynamic stability of a power system, based on the application of a variety of architecture and configurations of artificial neural networks. On the basis of the complete system state vector, which represents the input into a multi‐layered neural network, the topology detection of the transmission network is carried out. Depending on the operating regime ‐ the system topology and load level ‐ the corresponding multi‐layered neural network is activated in order to detect the stability of the system. Stability analysis is achieved by tracking changes in the dominant eigenvalues of the system which are the output of the trained neural network. Finally, the paper presents a means of analysing the dynamic stability of the power system on the basis of the reduced state vector, obtained by extraction of the characteristic state coordinates by means of self‐organizing neural network.
Fuse characteristics determined by melting or ageing?
Authors: Sloot J. G. J. , Meng X. Z. , Vermij L.
Published: July 2010

Fuses are designed to operate under fault conditions. However, because of ageing processes, fuses also operate in practice under normal load conditions. This article presents a method to determine how fuse characteristics change depending on specific load conditions. Based on metal fatigue laws, the process of ageing is described and compared with measurements. A method is proposed how to formulate general ageing behaviour from a limited number of measurements under specific conditions. The method is demonstrated for miniature fuses but also showed to be valid for fuses for the protection of motors and semiconductors.
Noise reduction in on‐site partial discharge measurement by the use of the transfer function
Authors: Weck K.‐H. , Weinel F.
Published: July 2010

On‐site partial discharge (PD) measurements are frequently affected by noise due to external disturbances. This, in particular, applies to PD measurements during after‐laying tests on cable systems. The paper describes a noise‐reduction method in which the PD signal is corrected corresponding to a simultaneously recorded signal from a not energized reference system using the transfer function between the two systems in the frequency domain. The number of calculation steps involved in the procedure could be minimized to an extent that solution operating in real‐time can be realized. The criteria necessary for such solutions are established.
Common and fixed‐poles resonant harmonic filters
Authors: Czarnecki L. S.
Published: July 2010

Distribution voltage harmonics corrupt the effectiveness of resonant harmonic filters in reducing waveform distortion. The same is with load current harmonics of frequencies other than those to which the filter is tuned. Low impedance for the distribution voltage harmonics and resonances of the filter with the inductance of the distribution system are responsible for degrading filter effectiveness. A Iso, a change in the supply system structure or parameters may affect filter effectiveness. Filter effectiveness improves when the harmful resonances of the filter with the system inductance, i. e. the poles of the filter transmittance, are sufficiently far from harmonic frequencies. This paper presents a method of synthesis of resonant harmonic filters with the poles located at the designer's discretion. A line inductor with an inductance of the order of the equivalent inductance of the distribution system reduces the dependence of filter performance on changes in the distribution system parameters. Such a filter is referred to as a fixed‐poles resonant harmonic filter. Filters designed with the method described in this paper have higher effectiveness and their performance is more predictable as compared to filters designed traditionally, referred to as common filters.
About the accuracy of some proposed procedures for revenue metering under non‐sinusoidal unbalanced conditions
Authors: Sasdelli R. , Ferrero A. , Menchetti A. , Peretto L.
Published: July 2010

In order to discourage the insertion of polluting loads, suitable tariff policies should be adopted. A possible strategy is based on the comparison between the total active power and the active power at fundamental frequency and positive sequence. Digital Signal Processing techniques allow for the implementation of revenue meters able to measure both those quantities and any index based on them. This paper analyses the accuracy that can be expected in the measurement of both the ratio and the difference of the above powers. The results of numerical simulations confirm that the ratio measurement is suitable for revenue purposes even when the total and fundamental active powers differ for parts per thousands.
Study of commutation phenomena and faults in a system consisting of a synchronous generator and a controlled rectifier
Authors: Kappatou J. , Safacas A.
Published: July 2010

The effect of the system parameters on the commutation phenomena in a system consisting of a synchronous generator, a controlled rectifier and a DC load is being studied in detail. Furthermore, the behaviour of the system in cases of failure of ignition and short circuit of a controlled semiconducting element, is being investigated. The system under study was simulated by a method appropriate for the simulation of variable topology networks.
Generalized method for fault simulations in power systems
Authors: Oswald B. R.
Published: July 2010

This paper presents a new generalized method of modelling of any kind of shunt and series faults as single or simultaneous faults in arbitrary combination. The proposed approach can be used for conventional fault studies for the steady‐state model based on the nodal admittance representation as well as for fault simulations under transient conditions by means of the EMTP/ATP program. This method has been developed for phase coordinates but it is also suitable for any modal coordinates. The purpose of this paper is to show the incorporation of these fault conditions in the EMTP/ATP algorithm.
Load‐flow conditions for hvdc transmission in synchronous networks
Authors: Warnking J. , Balzer G.
Published: July 2010

The basic purpose for HVDC (high‐voltage direct current) transmission is to transmit a determined value of electrical power from one electrical node to another. If there is an AC system in parallel to an HVDC transmission, the load flow via this parallel AC system can be controlled directly. Since HVDC systems offer possibilities to perform fast load‐flow control, they can also be used for improving stability. In this paper load‐flow calculations of a simplified network are presented. First a comparison between HVDC transmission operating in asynchronous resp. synchronous networks is shown. Synchronous network means that the HVDC transmission works in parallel to an AC system at the same voltage level. It is shown how voltage at the point of installation and how the load angle are influenced due to the synchronous operation. A special regard is drawn to the losses of the transmission. Conditions for minimum total losses are presented. Informer calculations loads are involved. It is shown how they influence the minimum total losses.
Economic dispatching with prohibited zones using an extended linear hopfield model
Authors: Chiou G.‐J. , Su C.‐T.
Published: July 2010

This paper proposes a fast Hopfield method with a dispatching strategy to resolve the economic dispatch (ED) problems constrained by prohibited zones. The prohibited operating zones of the units cause such ED problems to become non‐convex optimization ones. The proposed method employs a linear input‐output model for neurons, enabling the development of an operational model for rapidly resolving the ED problems. Applying the strategy to the prohibited zones problem encountered in the dispatching process allows the proposed method to achieve the optimal solution for the non‐convex problems. The effectiveness of the proposed approach is demonstrated by investigating a 15‐unit system with four units possessing prohibited zones. According to the results of the example, the proposed method is more efficient and versatile than the conventional Hopfield method.
A method of gamma‐beta durability determination for reliability tests of brand‐new AC electromagnetic contactors
Authors: Wróblewski Z.
Published: July 2010

In the paper a method of “gamma‐beta” durability determination of AC electromagnetic contactors is presented. Based on reliability models of essential contactor sub‐assemblies, the method enables to estimate durability of the “gamma” part of the overall contactor population at the specified confidence level “beta”. The method is meant for industrial laboratories which carry out reliability tests of brand‐new AC contactors.
Excitation control of a power‐generating system based on fuzzy logic and neural networks
Authors: Karnavas Y. L. , Papadopoulos D. P.
Published: July 2010

This paper presents a practical design of an intelligent controller (using fuzzy logic and neural network concepts) for the excitation control of an isolated power‐generating system. The controller is suitable for realtime operation, with the aim of improving the dynamic characteristics of the generating unit by acting properly on the exciter input. At first, digital simulations of high‐ and reduced‐order models of the above system are performed using conventional control techniques on five system cases which are based on previous work. Then, a fuzzy logic proportional‐plus‐derivative controller (FPDC) is designed and the dynamic performances of the mentioned five system cases and the FPDCs are presented by comparison. Finally, an enhanced controller is designed which involves a pre‐trained neural network as a model dynamics capture. The computer simulation results obtained clearly demonstrate that the performance of the developed fuzzy logic and neural network controller offers better damping effects on the generator oscillations over a wider range of operating conditions, than the associated ones of the conventional excitation controller designs with output feedback applied to high‐ and reduced‐order system models.
Influence of cathodic protection and transmission‐line proximity on oil‐flow electrification
Authors: Metwally I. A.
Published: July 2010

Two reduced‐scale closed oil cycles are used to investigate the influence of both the cathodic protection of a pipeline and its proximity to AC power transmission lines on the oil‐flow electrification (OFE). For the former case, the results reveal that the OFE is highly dependent on the magnitude of the protection current. The higher the protection voltage the higher is the OFE. Also, the results show that the OFE is enhanced by oil velocity and/or temperature. For the latter case, the results indicate that conductor bundling has a monumental impact on all measured quantities: pipe floating potential, and both corona and streaming currents. In addition, oil temperature causes evident quantitative as well as qualitative changes in the measured streaming current, but no effect was found on both pipe floating potential and corona current. The results are interpreted in terms of physico‐chemical and electrochemistry point of view together with electric field computation using a program based on charge simulation method.
Wind energy converter with asynchronous machines and three‐phase ac controller in generator mode
Authors: Rösner J. , Beck H. P. , Sourkounis C.
Published: July 2010

Wind energy converters (WEC) with an asynchronous generator are usually connected to the grid during start‐up time via a softstarter, consisting of a three‐phase AC controller. In generator mode the controller is bridged and the wind turbine is connected directly to the grid. In this case changes of wind speed cause fluctuations of the electrical power. This paper shows, how the controller can be used as a power controller with the aim of reducing the grid interference and life‐time extension for the mechanical components. In simulation and on a WEC‐model 10‐kW test bed it could be shown that the power control limits the power up current to the nominal current and both power fluctuations produced by wind speed variation and tower shadow effect are reduced. The harmonics were analysed and compared to the harmonics of a six‐phase generator and a twelve‐pulse AC controller.
Tests on the vibro‐acoustic behaviour of a brushless DC‐motor
Authors: Heylen W. , Desmet W. , Belmans R.
Published: July 2010

In the design of rotating electrical machines, the vibro‐acoustic behaviour becomes an important criterion. In an electrical machine, electromagnetically induced forces may cause vibrations of, for instance, the stator. These vibrations may radiate annoying acoustic energy, especially at resonances of the stator assembly. This paper describes some techniques to analyse the vibro‐acoustic behaviour of a (brushless DC‐) motor. However, the technique is quite general and can be used for all types of electrical machines. The “inverse‐frequency‐response‐function” technique (I FRF) allows the identification of the actual vibration behaviour of the motor frame from the measurement of the acoustic field around the motor. Experimental modal analysis yields the resonant behaviour of the motor. A combination of both techniques indicates the critical resonances, causing the undesired acoustic emissions. This may lead to an improved, quieter design of the electrical motor.
Direct torque control of synchronous motor drives for dynamically demanding applications
Authors: Pyrhönen J. , Pyrhönen O. , Niemelä M. , Luukko J. , Kaukonen J. , Pohjalainen P.
Published: July 2010

This paper proposes a new concept for the Direct‐Torque‐Control (DTC)‐based synchronous machine drive. DTC technology provides a synchronous machine drive with excellent dynamic properties. The DTC principles are first briefly recalled. The study observes the problem of the flux linkage integration instability and introduces the flux linkage estimate correction method based on the current model. The field winding current control methods are analysed. It is shown that a synchronous machine drive also needs a stabilisation method when working with very high load angles especially in the field weakening range. A method to control the load angle directly is then proposed. Test results with a 14.5‐kVA laboratory prototype drive are given.
Simplified d‐q dynamic models of the slip energy recovery drive
Authors: Papathanassiou S. A. , Papadopoulos M. P.
Published: July 2010

The issue of the d‐q dynamic modelling of the slip energy recovery drive is addressed in this paper. Two original d‐q dynamic models are presented, in which the harmonics and commutation phenomena of the rotor converters are neglected. The performance of these models, along with another one already used in the literature, is evaluated through comparison with a detailed model of the drive, involving the valve‐by‐valve representation of the converters. One of the novel d‐q models proves to be very satisfactory, achieving good accuracy in all cases, while the other two present increased errors for certain disturbances and operating conditions.
Chromosome band 17q21 in breast cancer: Significant association between beclin 1 loss and HER2/NEU amplification
Authors: Negri Tiziana , Tarantino Eva , Orsenigo Marta , Reid James F. , Gariboldi Manuela , Zambetti Milvia , Pierotti Marco A. , Pilotti Silvana
Published: June 2010

Treatment success of breast cancer patients with trastuzumab alone or in combination depends not only on HER2/NEU amplification but also on PTEN and PI3K status and efficient cell death programs. In this pilot study, we found a significant association between loss of beclin 1 and HER2/NEU amplification (both on 17q21) in breast cancers. This finding was confirmed in two public copy number microarray datasets. Furthermore, there is a trend associating beclin 1 loss with TP53 mutations, PI3KCA gene gain, and PTEN mutations. Finally, the observation that beclin 1 gene loss predicted a response to trastuzumab alone or in combination with other drugs is worthy of further confirmation in larger cohorts. Our results suggest that, beclin 1 loss may contribute to genome instability and to a defective autophagy that may lead to tumoral cell death in presence of competent apoptosis or senescence pathways. © 2010 Wiley‐Liss, Inc.
Assessing the value of high‐resolution isotope tracer data in the stepwise development of a lumped conceptual rainfall–runoff model
Authors: Birkel C. , Dunn S. M. , Tetzlaff D. , Soulsby C.
Published: June 2010

A study was undertaken in a small agricultural catchment in north east Scotland with the objective of assessing the value of high‐resolution isotope data for integration within a lumped, conceptual hydrological model to improve calibration and aid evaluation. Daily samples of precipitation and stream flow, collected over a year, were analysed for deuterium using new laser spectroscopy technology. The utility of such high‐resolution isotope data was evaluated in relation to the associated uncertainty which was contextualized in relation to uncertainties over hydrometric data and the influence of different sampling resolutions. The simulations were evaluated against model and data errors using auxiliary stream deuterium time series in addition to discharge. The lumped conceptual catchment isotope model (CIM) was developed and adequately reflects flow dynamics and deuterium peaks, but a simple assumption of ‘good mixing’ is not able to fully reproduce the daily stream deuterium dynamic. Using auxiliary data for model evaluation, however, significantly constrained acceptable behavioural parameter sets and therefore reduces the model's degree of freedom. The data indicate that isotopic variability in the stream response is not adequately captured using weekly tracer data. The input resolution of precipitation deuterium concentrations, which were much more variable, proved to be crucial. This approach has provided further assessment of the value of tracers in hydrological modelling, demonstrating their usefulness in terms of model conceptualization, development and calibration, which outweighs the additional uncertainty. Copyright © 2010 John Wiley & Sons, Ltd.
Overview of the nonclinical quality and toxicology testing for recombinant biopharmaceuticals produced in mammalian cells
Authors: Lebrec Hervé , Narayanan Padma , Nims Raymond
Published: June 2010

Biopharmaceuticals represent significant advances in therapeutic approaches for unmet medical needs, and increasingly, traditional pharmaceutical firms have been incorporating biotechnology capabilities into their product portfolios. There are some differences in the overall safety testing paradigms for small molecules and biopharmaceuticals, this safety testing including both quality and toxicology aspects. These differences are associated with both the manufacturing processes involved and the molecules themselves. For example, for biopharmaceuticals, living cells represent the factories for synthesizing complex molecular entities. As a result of this, safety testing for this class of drugs includes adventitious agent testing (e.g. viral, mycoplasma, transmissible spongiform encephalopathy agents) not normally needed for small molecules. Also, strategies for nonclinical toxicology testing of biopharmaceuticals differ from the paradigms used for small molecules and often need to be defined on a case‐by‐case basis, primarily taking into consideration species cross‐reactivity attributes of the molecule of interest. Certain studies required for small molecules are not applicable to most biopharmaceuticals (i.e. genotoxicity testing, testing for interactions with the hERG channel). This manuscript provides an overview of both the quality and nonclinical toxicology testing for these mammalian‐cell‐derived products, two elements pivotal to the overall nonclinical assessment of the safety of these biopharmaceutical products. Copyright © 2010 John Wiley & Sons, Ltd.
p53 control of bone remodeling
Authors: Liu Huijuan , Li Baojie
Published: June 2010

Tumor suppressor p53 is a transcription regulator that displays anti‐proliferation activities once activated by stress, in particular genotoxic stress. Recent mouse genetic studies revealed a critical role for p53 in bone remodeling, supported by both loss‐of‐function and gain‐of function studies. p53 deficiency concurrently enhances proliferation and accelerates differentiation in mesenchymal stem cells and osteoprogenitor cells, resulting in an increase in bone formation and bone mass/density. Moreover, Atm, c‐Abl, and Mdm2, upstream regulators of p53 in DNA damage response, regulate osteoblast differentiation and bone remodeling as well. While the molecular mechanisms await further investigation, there is evidence to suggest that p53 regulate osteoblast differentiation via transcription factors Runx2/Osterix, which are involved in osteoblast differentiation and transformation and are under the control of BMP and IGF pathways. Moreover, there are studies showing that p53 inhibits cell differentiation in many other tissues. These findings suggest that p53 acts as a safeguard of differentiation in addition to “guardian of the genome” and challenge the conventional wisdom that tumor suppressors usually block cell proliferation and promote differentiation. J. Cell. Biochem. 111: 529–534, 2010. © 2010 Wiley‐Liss, Inc.
Syntaxin 16: Unraveling cellular physiology through a ubiquitous SNARE molecule
Authors: Chen Yanan , Gan Bin Qi , Tang Bor Luen
Published: June 2010

Syntaxin 16 (Syx16) is member of the soluble N‐ethylmaleimide sensitive factor attachment protein receptor (SNARE) family of molecules that functions in membrane fusion in eukaryotic cells. A rather ubiquitously expressed, tail‐anchored membrane protein localized mainly at the trans‐Golgi network (TGN), it mediates primarily retrograde endosomal‐TGN transport. In spite of its ubiquitous expression, Syx16 has specific and interesting roles in the physiology of specialized cells, including Glut4 dynamics, dendritic outgrowth‐related membrane traffic, and cytokinesis. We discussed these physiological functions of Syx16 in the light of what is known of its subcellular localization, vesicular trafficking pathways involved, cognate SNARE partners and other interacting proteins. Further, we speculate on some possible pathophysiological roles of Syx16. J. Cell. Physiol. 225: 326–332, 2010. © 2010 Wiley‐Liss, Inc.
Regulation of MT1‐MMP activity by β‐catenin in MDCK non‐cancer and HT1080 cancer cells
Authors: Liu Ping , Yang Jianbo , Pei Jing , Pei Duanqing , Wilson Michael J.
Published: June 2010

Past studies on β‐catenin in cancer cells focused on nuclear localized β‐catenin and its involvement in the Wnt pathway. Our goal here was to investigate the function of β‐catenin in both the cytoplasm and nucleus on the regulation of MT1‐MMP expression and activity. We found that β‐catenin in MDCK non‐cancer cells inhibited the cell surface localization of MT1‐MMP, and thus its proteolytic activity on pro‐MMP2 activation, via direct interaction with the 18‐amino‐acid cytoplasmic tail of MT1‐MMP in the cytoplasm. In contrast, β‐catenin in HT1080 cancer cells enhanced the activity of MT1‐MMP by entering the nucleus and activating transcription factor Tcf‐4/Lef, and elevating the level of MT1‐MMP protein. We also found that enhancement of cell growth in three‐dimensional (3‐D)/two‐dimensional (2‐D) type I collagen gels and of cell migration by MT1‐MMP were inhibited by β‐catenin in MDCK cells, whereas these functions were enhanced in HT1080 cells. In addition, regulation of MT1‐MMP by β‐catenin involved E‐cadherin in MDCK cells and Wnt‐3a in HT1080 cells. Taken together, our results present a differential effect of cytoplasmic and nuclear β‐catenin on MT1‐MMP activity in non‐cancer cells versus cancer cells. These differences were most probably due to different subcellular locations and different involved pathways of β‐catenin in these cells. J. Cell. Physiol. 225: 810–821, 2010. © 2010 Wiley‐Liss, Inc.
The relation between emotional intelligence and job performance: A meta‐analysis
Authors: O'Boyle Ernest H. , Humphrey Ronald H. , Pollack Jeffrey M. , Hawver Thomas H. , Story Paul A.
Published: June 2010

This meta‐analysis builds upon a previous meta‐analysis by (1) including 65 per cent more studies that have over twice the sample size to estimate the relationships between emotional intelligence (EI) and job performance; (2) using more current meta‐analytical studies for estimates of relationships among personality variables and for cognitive ability and job performance; (3) using the three‐stream approach for classifying EI research; (4) performing tests for differences among streams of EI research and their relationships with personality and cognitive intelligence; (5) using latest statistical procedures such as dominance analysis; and (6) testing for publication bias. We classified EI studies into three streams: (1) ability‐based models that use objective test items; (2) self‐report or peer‐report measures based on the four‐branch model of EI; and (3) “mixed models” of emotional competencies. The three streams have corrected correlations ranging from 0.24 to 0.30 with job performance. The three streams correlated differently with cognitive ability and with neuroticism, extraversion, openness, agreeableness, and conscientiousness. Streams 2 and 3 have the largest incremental validity beyond cognitive ability and the Five Factor Model (FFM). Dominance analysis demonstrated that all three streams of EI exhibited substantial relative importance in the presence of FFM and intelligence when predicting job performance. Publication bias had negligible influence on observed effect sizes. The results support the overall validity of EI. Copyright © 2010 John Wiley & Sons, Ltd.

Note: Correction added on 22 July 2010 after first publication online on 29 June 2010. The affiliations for Ronald H. Humphrey and Thomas H. Hawver have been corrected in this version of the article.
Preparative enrichment and separation of astragalosides from Radix Astragali extracts using macroporous resins
Authors: Kong Yu , Yan Ming‐Ming , Liu Wei , Chen Cai‐Yun , Zhao Bao‐Shan , Zu Yuan‐Gang , Fu Yu‐Jie , Luo Meng , Wink Michael
Published: June 2010

The enrichment and separation of astragalosides I–IV (AGs I–IV) were studied on eight macroporous resins in the present study. SA‐3 resin offered the best adsorption and desorption capacities for AGs I–IV than other resins. The models of adsorption kinetics were investigated in order to elucidate the mechanism of adsorption. The pseudo‐second‐order model was the better choice than the pseudo‐first‐order model to describe the adsorption behavior of AGs I–IV onto SA‐3 resin. The equilibrium experimental data were well fitted to Langmuir and Freundlich isotherms. SA‐3 resin adsorption chromatography tests were carried out to optimize the separation process of AGs I–IV from Radix Astragali extracts. With the optimum parameters for adsorption and desorption, the contents of AGs I–IV were 8.78‐, 11.60‐, 10.52‐ and 11.28‐fold increased with the recovery yields being 65.88, 90.92, 84.25 and 94.17%, respectively. The preparative enrichment and separation of AGs I–IV from Radix Astragali extracts can be easily and effectively achieved by SA‐3 resin adsorption chromatography. The developed methodology can also be referenced for the separation of other active constituents from herbal materials and manufacture of Radix Astragali products.
Determination of ergot alkaloids from grains with UPLC‐MS/MS
Authors: Kokkonen Meri , Jestoi Marika
Published: June 2010

A simple and rapid method for determining six ergot alkaloids and four of their respective epimers was developed for rye and wheat. The analytes were extracted from the sample matrix with ACN/ammonium carbonate solution. The extract was purified with a commercial push‐through SPE column (Mycosep® 150 Ergot). After concentration and filtration steps, the final separation of the analytes was achieved with ultra‐performance LC‐MS/MS. The chromatographic separation of the ergot alkaloids was achieved in 4.5 min. The method performance proved satisfactory in the preliminary validation. The calculated LOQs were low ranging from 0.01 to 1.0 μg/kg for wheat and from 0.01 to 10.0 μg/kg for rye. At the concentration levels of 10, 50 and 200 μg/kg, the recoveries were between 80 and 120% in most cases and the within‐day repeatability (expressed as RSD) ranged between 1.3 and 13.9%. Despite the cleanup of the samples, some matrix effect was observed in the MS, highlighting the necessity of using matrix‐assisted standards. This is the first article to describe the application of the push‐through columns and ultra‐performance LC in the analysis of ergot alkaloids.
Extraction of crocin from saffron (Crocus sativus) using molecularly imprinted polymer solid‐phase extraction
Authors: Mohajeri Seyed Ahmad , Hosseinzadeh Hossein , Keyhanfar Fariborz , Aghamohammadian Javad
Published: June 2010

A new molecularly imprinted polymer for extraction of crocin from saffron stigmas was prepared using gentiobiose (a glycoside moiety in crocin structure) as a template. Crocin binding to gentiobiose imprinted polymer (Gent‐MIP) was studied in comparison with a blank nonimprinted polymer in aqueous media. Affinity of the Gent‐MIP for the crocin was more than the nonimprinted polymer at all concentrations. In Scatchard analysis, the number of binding sites in each gram of polymer (maximum binding sites) and dissociation constant of crocin to binding sites were 18.4 μmol/g polymer and 11.2 μM, respectively. The Gent‐MIP was then used as the sorbent in an SPE method for isolation and purification of crocin from methanolic extract of saffron stigmas. The recovery of crocin, safranal and picrocrocin was determined in washing and elution steps. The Gent‐MIP had significantly higher affinity for crocin than other compounds and enabled selective extraction of crocin with a high recovery (84%) from a complex mixture. The results demonstrated the possibility of using a part of a big molecule in preparing a molecularly imprinted polymer with a good selectivity for the main structure.