Single Test System Research Articles

Single network adaptive critic design for power system stabilisers

The recently developed single network adaptive critic (SNAC) design has been used in this study to design a power system stabiliser (PSS) for enhancing the small-signal stability of power systems over a wide range of operating conditions. PSS design is formulated as a discrete non-linear quadratic regulator problem. SNAC is then used to solve the resulting discrete-time optimal control problem. SNAC uses only a single critic neural network instead of the action-critic dual network architecture of typical adaptive critic designs. SNAC eliminates the iterative training loops between the action and critic networks and greatly simplifies the training procedure. The performance of the proposed PSS has been tested on a single machine infinite bus test system for various system and loading conditions. The proposed stabiliser, which is relatively easier to synthesise, consistently outperformed stabilisers based on conventional lead-lag and linear quadratic regulator designs.

Responses of three benthic organisms (Hyallela azteca, Limnodrillus hoffmeisteri and Stagnicola attenuata) to natural sediment spiked with zinc when exposed in single or multi-species test systems

In order to determine the influence of the presence of one or more species in a system on Zn toxic response, acute (LC50 at 72 h) and sublethal toxicity (Zn uptake kinetics, and quantification of total protein content and lipid peroxidation levels) were evaluated in three benthic organisms (Hyallela azteca, Limnodrillus hoffmeisteri and Stagnicola attenuata). They were exposed either singly or together (single or multi-species test systems) to Zn-spiked sediment from Ignacio Ramírez Reservoir. Both assays showed that Zn-spiked sediments from Ignacio Ramírez Reservoir were toxic to S. attenuata, L. hoffmeisteri and H. azteca, and that toxic response was modified according to the number of species in the system. These differences may be due to multiple factors: such as benthic bioturbation which modifies physical and chemical characteristics of sediments and affects the fate and partitioning of sediment-bond contaminants, such as spiked Zn or other pollutants in sediments from Ignacio Ramírez Reservoir. In addition, the presence of more than one species in the system may lead to microenvironmental changes (pH, temperature, and organic matter and metabolic waste content), which can also contribute to toxic response differences. Also, particular characteristics of each of the species involved in the study became evident. The snail and amphipod are facultative benthic organisms, while the worm is obligate. Such way of life differences may have modified the bioavailability of contaminants, determining their toxicity.

Genetic Toxicity Assessment: Employing the Best Science for Human Safety Evaluation Part VII: Why Not Start with a Single Test: A Transformational Alternative to Genotoxicity Hazard and Risk Assessment

A transformational alternative for genotoxicity hazard and risk assessment is proposed to the current standard regulatory test battery. In principle, the proposed approach consists of a single in vitro test system with high genomic sequence homology to humans that addresses the relevant principal genetic lesions assessed in the current test battery. The single test system also possesses higher throughput attributes to permit the screening of large numbers of compounds and allow for an initial differentiation of genotoxic mechanisms (i.e., direct vs. indirect mechanisms) by how the hazard end point is measured. To differentiate compounds showing positive results, toxicogenomic analysis can be conducted to evaluate genotoxic mechanisms and further support risk assessment. Lastly, the results from the single test system can be followed up with a complementary in vivo assessment to establish mechanistic relevance at potential target tissues. Here, we propose the in vitro (yeast) DNA deletion (DEL) recombination assay as a single test alternative to the current genotoxicity test battery with a mechanistic follow up toxicogenomic analysis of genotoxic stress response as one approach that requires broader evaluation and validation. In this assay, intrachromosomal recombination events between a repeated DNA sequence lead to DNA deletions, which have been shown to be inducible by a variety of carcinogens including those both negative and positive in the standard Salmonella Ames assay. It is hoped that the general framework outlined along with this specific example will provoke broader interest to propose other potential test systems.

Factors influencing timing resolution in a commercial LSO PET camera

The CPS Accel is a commercial PET camera based on a block detector with 64 LSO scintillator crystals (each 6.75/spl times/6.75/spl times/25 mm) read out with 4 photomultiplier tubes. The excellent timing resolution of LSO suggests that this camera might be used for time-of-flight (TOF) PET, thereby reducing the statistical noise significantly. Although the Accel achieves 3 ns coincidence resolution (a factor of two better than BGO-based PET cameras), its timing resolution is nearly an order of magnitude worse than that demonstrated with individual LSO crystals. This paper quantifies the effect on the timing of each component in the Accel timing chain to identify which components most limit the camera's timing resolution. The components in the timing chain are: the scintillator crystal, the photomultiplier tube (PMT), the constant fraction discriminator (CFD), and the time to digital converter (TDC). To measure the contribution of each component, we construct a single crystal test system with high-performance versions of these components. This system achieves 221 ps FWHM coincidence timing resolution, which is used as a baseline measurement. One of the high-performance components is replaced by a production component, the coincidence timing resolution is re-measured, and the difference between measurements is the contribution of that (production) component. We find that the contributions of the TDC, CFD, PMT, and scintillator are 2000 ps, 1354 ps, 422 ps, and 326 ps FWHM, respectively, and that the overall timing resolution scales like the square root of the amount of scintillation light detected by the PMT. Based on these measurements we predict that the limit for the coincidence timing resolution in a practical, commercial, LSO-based PET camera is 528 ps FWHM.

Stochastic model updating: Part 1—theory and simulated example

The usual model updating method may be considered to be deterministic since it uses measurements from a single test system to correct a nominal finite element model. There may however be variability in seemingly identical test structures and uncertainties in the finite element model. Variability in test structures may arise from many sources including geometric tolerances and the manufacturing process, and modelling uncertainties may result from the use of nominal material properties, ill-defined joint stiffnesses and rigid boundary conditions. In this paper, the theory of stochastic model updating using a Monte-Carlo inverse procedure with multiple sets of experimental results is explained and then applied to the case of a simulated three degree-of-freedom system, which is used to fix ideas and also to illustrate some of the practical limitations of the method. In the companion paper, stochastic model updating is applied to a benchmark structure using a contact finite element model that includes common uncertainties in the modelling of the spot welds.

Three-dimensional quantitative structure-activity relationship analyses of peptide substrates of the mammalian H+/peptide cotransporter PEPT1.

The utilization of the carrier protein PEPT1 for the absorption of peptidomimetic drug molecules is a promising strategy for oral drug administration and increasing bioavailability. In the absence of structural information on the binding mode of substrates to PEPT1, a computational study was conducted to explore the structural requirements for substrates and to derive a predictive model that may be used for the design of novel orally active drugs. A comparative molecular field analysis (CoMFA) and a comparative molecular similarity indices analysis (CoMSIA) were performed on a series of 79 dipeptide-type substrates for which affinity data had been collected in a single test system under the same conditions. These studies produced models with conventional r(2) and cross-validated coefficient (q(2)) values of 0.901 and 0.642 for CoMFA and 0.913 and 0.776 for CoMSIA. The models were validated by an external test set of 19 dipeptides and dipeptide derivatives. CoMSIA contour maps were used to identify the recognition elements that are relevant for the binding of PEPT1 substrates. The 3D QSAR models provide an insight in the interactions between substrates and PEPT1 on the molecular level and allow the prediction of affinity constants of new compounds.

Core losses in claw pole permanent magnet machines with soft magnetic composite stators

This paper presents the core loss calculation in soft magnetic composite (SMC) samples and a claw pole permanent magnet machine with SMC stator. By using finite-element analysis of the magnetic field, the total core loss is computed by separating the hysteresis (alternating and rotational, both purely circular and elliptical), eddy current, and anomalous losses in each element when the rotor rotates. The coefficients for each loss component are determined by a loss separation procedure and the experimental data obtained by a single sheet two-dimensional core loss testing system.

Enhancement of power system damping using VSC-based series connected FACTS controllers

An equivalent model is proposed to analyse the capabilities of voltage source converter (VSC)-based series connected flexible AC transmission system (FACTS) controllers of various types to damp power system oscillations. A universal control strategy using a fuzzy logic method is developed for controlling these VSC-based series connected FACTS controllers. Only the magnitude of the injected voltage needs to be controlled, along with its phase angle which is always set to be constant at π/2 with respect to different reference voltage vectors for the different controllers. Local measurable signal — voltage phase angle difference between two local buses — is selected as an input base. Two inputs, namely the speed rate and acceleration, derived from the phase angle difference, are required for the fuzzy controller, which is robust and easy to tune, to damp power system oscillations. Case studies for a single machine infinite bus (SMIB) and two-machine test systems are conducted at the switch level using the well-established PSCAD/EMTDC software package.

Intact follicle culture: what it can tell us aabout the roles of FSH glycoforms during follicle development

An important limiting factor in assisted reproduction treatment success rates is oocyte quality. In spite of improved results through several important innovations, the pregnancy rate per collected oocyte remains far too low. In order to improve this situation, it is necessary to learn more about fundamental factors modulating follicular development patterns. FSH is known to be the driving force for follicle development, but it is not yet understood how its multifarious functions are controlled and modulated. Evidence is accumulating that FSH glycoforms may be the key to this mystery. Intact follicle culture is a useful tool for the clarification of the actions of the different isoforms because the follicle unit is maintained and allowed to develop through several critical stages. Additionally important is the availability of the oocyte for functional evaluation. Because of these features, relationships can be uncovered that are not revealed with single cell test systems. The results so far obtained with this system suggest that follicle development pattern and oocyte quality is strongly influenced by FSH glycoform range, and that the requirements of the follicle may shift during progress through different stages of development. More studies are required, but these findings already suggest that the physiological shifts of circulating FSH glycoforms may indeed be important, and that attention should be paid to the glycoform distribution of exogenously applied FSH.

Determination of the antioxidative potential of human plasma after supplementation with pycnogenol and whey

The aim of this study was to determine the antioxidative properties of human blood plasma utilised in six different biochemical in vitro test systems and to investigate the supplementation of human blood plasma with Pycnogenol and whey powder in three out of these six systems. Furthermore was the copper induced LDL-oxidation used. It is shown that plasma indicates a varied antioxidative capacity in the six systems used depending on the ROS generated in the single test system. To enhance the antioxidative properties of plasma it can be supplemented with polyphenols, which are known to act as antioxidants. Hence a mixture of different polyphenols would be a great opportunity and is given in the extract of pine bark, Pycnogenol. The supplementation of plasma with Pycnogenol and whey powder exhibits the possibility to use whey as a carrier for Pycnogenol, not reducing the properties of Pycnogenol, instead achieving an additive effect.

Textural Characterization and Kinetics of Potato Strips During Frying

ABSTRACT: A single puncture test (SPT) system was designed to determine textural changes in potato strips in situduring frying at 160, 175, and 190 °C. Puncture force changed drastically with time and depth in the strip during frying. Force‐distance curves were expressed as representative textural parameters as CF (core force), RF (rupture force), and S (springiness). Normalized parameters CF* and S* for core force and springiness were used in modeling textural changes in the core during initial tissue softening and later crust development process, respectively. High frying temperatures accelerated the process, and the finished fried potato strip was a composite structure made of a hard crust and a soft core.

Antimicrobial susceptibility testing: special needs for fastidious organisms and difficult-to-detect resistance mechanisms.

Clinical microbiology laboratories are faced with the challenge of accurately detecting emerging antibiotic resistance among a number of bacterial pathogens. In recent years, vancomycin resistance among enterococci has become prevalent, as has penicillin resistance and multidrug resistance in pneumococci. More recently, strains of methicillin-resistant Staphylococcus aureus with reduced susceptibility to vancomycin have been encountered. In addition, molecular techniques have demonstrated that there are still problems detecting methicillin resistance in staphylococci, especially in coagulase-negative species. Among members of the family Enterobacteriaceae, mutated beta-lactamase enzymes may confer difficult-to-detect resistance to later-generation penicillins and cephalosporins. Anaerobic bacteria are no longer entirely predictable in their susceptibility to agents that might be selected for empiric therapy. Therefore, clinical microbiology laboratories may not be able to rely on a single susceptibility testing method or system to detect all those emerging resistant or fastidious organisms. For reliable detection, laboratories may need to employ conventional, quantitative susceptibility testing methods or use specially developed, single concentration agar screening tests for some resistant species. Certain of these screening tests are highly specific, while others may require additional confirmatory testing for definitive results. Therefore, laboratories must retain the versatility to apply several different approaches to detect resistance in both common and infrequently encountered bacterial pathogens.

Quality systems for unit-use testing devices

Unit-use testing or single-test-system analysis has existed for many years. Quality-control and quality-assurance procedures have generally used conventional methods and lyophilized or aqueous control materials. Because these materials were readily available and generally accepted, they became part of the quality-assurance program for many early unit-use test systems such as the DuPont aca. Over the years, these control products became standard and are now required as part of good laboratory practice. Technically speaking, however, conventional quality-control methods and materials cannot completely control the test system when used in a unit-use or single-test-system device. When conventional control material is run on a unit-use single-test system, only that testing unit is checked. One cannot test every unit with control material because by definition these are single-test systems: Once the control has been run, the patient's sample cannot be run. Conventional quality-assurance and quality-control methods do not, of themselves, assure quality. A one-size-fits-all, or "two levels per day of use" as outlined in the CLIA '88 regulations, is not appropriate. The divergence between HCFA-approved practices and those of the deemed agencies, coupled with the financial aspects of this quality-control method, led to the formation of the Subcommittee on Unit Use Testing of the National Committee on Clinical Laboratory Standards to develop guidelines for manufacturers, users, and regulators to use in developing new quality systems.

Effects of an anionic surfactant, linear alkylbenzene sulfonate, on survival, reproduction and growth of the soil-living collembolanFolsomia fimetaria

Sewages sludge is widely used as a fertilizer or disposed of by land application. Sewage sludge often contains potentially toxic compounds and elements in significant concentrations. A major component is the anionic detergent, linear alkylbenzene sulfonate (LAS), which is frequently used in industrial and household detergents, and which may be found in the range 4 to 10 g kg−1 dry matter. The effects of LAS on Folsomia fimetaria L. were investigated by use of a single species test system with 30 g soil spiked with LAS. Tests with either newly hatched individuals or adults (16–19 d old) were run for 3 weeks followed by extraction in a high-gradient extracting system. Juvenile mortality increased with increasing concentrations of LAS, whereas adult mortality was unaffected at the LAS levels tested (0–1,000 mg/kg dry soil). Effective concentration, 10%, values were estimated as 163 mg/kg for growth of juveniles, 185 mg/kg for molting frequency, and 147 mg/kg for reproductive output. Rough estimates show that significant negative direct effects on populations of F. fimetaria may be expected at concentrations 8 to 20 times higher than those likely to be found in sludge-amended soils.

Development of Cyclic Triaxial Apparatus with Broad Frequency and Strain Ranges

A cyclic triaxial testing system capable of measuring very small to large strain properties on a single specimen has been developed by combining a wide variety of existing instrumentation, including piezoceramic bender elements, internal displacement measurement devices (both contact and noncontact), local displacement measurement devices, a sensitive internal load cell, and an external load cell. The bender elements provide information on soil properties in the nearly linear elastic (very small strain) range. Local and noncontact internal displacement measurements provide information about small strain range properties, whereas more traditional internal displacement measurements provide information in the small to large strain range. In addition, this apparatus can be used over a wide range of loading frequencies to investigate the effect of frequency on dynamic soil properties. By combining this equipment in a single testing system, a number of tests may be run on one specimen, eliminating the effects of variability. The broad variety of displacement measuring instruments also allows direct comparisons of these techniques on a single specimen.

Development of Cyclic Triaxial Apparatus with Broad Frequency and Strain Ranges

A cyclic triaxial testing system capable of measuring very small to large strain properties on a single specimen has been developed by combining a wide variety of existing instrumentation, including piezoceramic bender elements, internal displacement measurement devices (both contact and noncontact), local displacement measurement devices, a sensitive internal load cell, and an external load cell. The bender elements provide information on soil properties in the nearly linear elastic (very small strain) range. Local and noncontact internal displacement measurements provide information about small strain range properties, whereas more traditional internal displacement measurements provide information in the small to large strain range. In addition, this apparatus can be used over a wide range of loading frequencies to investigate the effect of frequency on dynamic soil properties. By combining this equipment in a single testing system, a number of tests may be run on one specimen, eliminating the effects of variability. The broad variety of displacement measuring instruments also allows direct comparisons of these techniques on a single specimen.

Mixed signal test — techniques, applications and demands

The increasing importance of next generation test technology to provide high quality, low cost fault detection methodologies is becoming a big issue in the microelectronics industry. For digital ASICs, techniques such as I-ddq and built-in-self test are being introduced to supplement or in some cases replace stuck-at-testing that has been shown to be inadequate for the circuit complexities and quality levels demanded. For analogue and mixed signal ICs, a similar trend is evident. Increasing circuit complexity, higher performance and the demand for high quality levels is causing the industry to question currently used functional and specification based test programs. In addition, the escalating costs of production test equipment capable of measuring high performance device parameters is in many cases becoming a limiting factor. The authors review the current state-of-the-art in mixed signal and analogue test technology with particular reference to the consumer electronics industry. Trends in key issues such as design-for-test, fault simulation, defect detection, CAD and tester support are discussed and the possible future role of these techniques is proposed for the next generation of single chip analogue and mixed signal test systems.

Biotesting wastewater for hazard evaluation

Evaluation of the potential hazard of treated water can be performed in two basic ways: chemical identification followed by chemical-by-chemical hazard summation or by means of biotesting the water as if the contaminants were a single compound. Current practice is somewhere in between. For the most part, the use of bioassays is limited to a single test system, and the results are usually interpreted as either positive or negative. That is, binary information is the usual result of a bioassay evaluation. Our work over the past decade has facilitated the development of an alternative approach to interpreting bioassay results. The key element in our approach is the use of relative comparisons. Relative comparisons between responses of a given test system using wastewater and a well-known agent allow a graded response for each different bioassay. By using a battery of different bioassay systems, each with different mechanisms of toxicity, we are able to characterize the composite toxicological response to a wastewater sample with respect to a well-studied “reference” chemical. The value of this approach is that, if the use of the reference chemical has acceptable risk to the majority of the population or at least a known human risk, the wastewater can be evaluated with respect to that factor. We use water chlorination as a “reference” material in this report to illustrate the concept.

Assessment and evaluation of genotoxicity findings

It is accepted in genetic toxicology that no single test system is capable of predicting with satisfactory reliability the genotoxic effects of a substance in humans. For this reason, test batteries are used when testing substances for possible genotoxic effects. The significance of the findings obtained can be clarified in three stages: interpretation of individual findings, assessment of genotoxicity data and evaluation with regard to the consequences on humans and the environment. Although these steps, which actually tend to merge into one another, cannot be strictly separated in practice, their differences must not be allowed to become too blurred and, in particu-

A non-enwrapping, single yoke on-line magnetic testing system for use in the steel industry

A nonenwrapping, single yoke, online magnetic testing system for measuring the magnetic properties of electrical steels in the steel industry has been developed. The magnetizing conditions within the arrangement have been investigated. Various methods of conveniently measuring the secondary voltages have also been studied. Various types of noncontact search coils for measuring flux density have been investigated. It is shown that a nonsolid search coil can be used as a secondary coil. Losses measured with the system agreed to within +or-5% of the results obtained using an Epstein frame.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>