Multiple Test Conditions Research Articles

Metal mixture modeling evaluation project: 3. Lessons learned and steps forward.

A comparison of 4 metal mixture toxicity models (that were based on the biotic ligand model [BLM] and the Windermere humic aqueous model using the toxicity function [WHAM-FTOX ]) was presented in a previous paper. In the present study, a streamlined version of the 4 models was developed and applied to multiple data sets and test conditions to examine key assumptions and calibration strategies that are crucial in modeling metal mixture toxicity. Results show that 1) a single binding site on or in the organism was a useful and oftentimes sufficient framework for predicting metal toxicity; 2) a linear free energy relationship (LFER) for bidentate binding of metals and cations to the biotic ligand provided a good first estimate of binding coefficients; 3) although adjustments in metal binding coefficients or adjustments in chemical potency factors can both be used in model calibration for single-metal exposures, changing metal binding coefficients or chemical potency factors had different effects on model predictions for metal mixtures; and 4) selection of a mixture toxicity model (based on concentration addition or independent action) was important in predicting metal mixture toxicity. Moving forward, efforts should focus on reducing uncertainties in model calibration, including development of better methods to characterize metal binding to toxicologically active binding sites, conducting targeted exposure studies to advance the understanding of metal mixture toxicity, and further developing LFERs and other tools to help constrain the model calibration.

A Resealable, Gas-Tight Packaging Technique for Silicon Microfluidic Devices

Recent efforts have led to the development of a silicon microfluidic cooling device known as the microcolumnated loop heat pipe (μCLHP). The μCLHP, like a traditional heat pipe, utilizes phase change of a liquid to rapidly draw heat away from a concentrated hot spot. Proper gas-tight packaging of this device is critical for the reliable testing of the recirculating fluid. This work presents a novel approach to filling and sealing the μCLHP. A miniature valve (Beswick M3SV-N) is bonded to the silicon fill ports of the μCLHP. The use of a resealable valve, as opposed to a permanent sealing method, allows the device to be filled, sealed, and then evacuated for testing with different fluids and at multiple pressures. Building on earlier work, the fill ports on the μCLHP were metalized with a Cr (10 nm)/Ni (200 nm)/Au (10 nm) stack. Then a lead-based solder was used to bond the stainless steel adapter to the metalized layers. Leak testing of devices sealed using these miniature valves demonstrated average hourly percent weight losses between 0.17% and 0.82%. While this bonding method has been developed specifically for the μCLHP, it is broadly applicable to most ceramic microfluidic devices, especially those fabricated from silicon and glass. Due to the time-intensive manufacturing process of microfluidic devices made from these hard materials, a novel, robust, resealing method that allows reuse of a single silicon microfluidic device for multiple test conditions is highly desirable.

A Resealable Hermetic Packaging Technique for Silicon Microfluidic Devices

Recent efforts have lead to the development of a silicon microfluidic cooling device known as the micro-Columnated Loop Heat Pipe (μCLHP) [1] [2] [3] . The μCLHP, like a traditional heat pipe, utilizes phase change of a liquid to rapidly draw heat away from a concentrated hot spot. Proper hermetic packaging of this device is critical for the reliable testing of the recirculating fluid. This work presents a novel approach to filling and hermetically sealing the μCLHP. A miniature valve (Beswick M3SV-N) is bonded to the silicon fill ports of the μCLHP. The use of a resealable valve, as opposed to a permanent sealing method, allows the device to be filled, sealed, and then evacuated for testing with different fluids and at multiple pressures. Building on work by Murphy [4], the fill ports on the μCLHP were metalized with a 10nm Cr - 200 nm Ni - 10 nm Au stack. Then a lead based solder was used to bond the stainless steel adapter to the metalized layers. Hermeticity testing of devices sealed using these miniature valves demonstrated average hourly percent weight losses between 0.170 % – 0.821 %. While this bonding method has been developed specifically for the μCLHP, it is broadly applicable to most ceramic microfluidic devices, especially those fabricated from silicon and glass. Due to the time intensive manufacturing process of microfluidic devices made from these hard materials, a novel, robust, resealing method that allows reuse of a single silicon microfluidic device for multiple test conditions is highly desirable.

All of the above: When multiple correct response options enhance the testing effect

Previous research has shown that multiple choice tests often improve memory retention. However, the presence of incorrect lures often attenuates this memory benefit. The current research examined the effects of “all of the above” (AOTA) options. When such options are correct, no incorrect lures are present. In the first three experiments, a correct AOTA option on an initial test led to a larger memory benefit than no test and standard multiple choice test conditions. The benefits of a correct AOTA option occurred even without feedback on the initial test; for both 5-minute and 48-hour retention delays; and for both cued recall and multiple choice final test formats. In the final experiment, an AOTA question led to better memory retention than did a control condition that had identical timing and exposure to response options. However, the benefits relative to this control condition were similar regardless of the type of multiple choice test (AOTA or not). Results suggest that retrieval contributes to multiple choice testing effects. However, the extra testing effect from a correct AOTA option, rather than being due to more retrieval, might be due simply to more exposure to correct information.

Investigation of tigecycline bactericidal activity: Optimisation of laboratory testing.

The objectives of this study were to optimise the conditions for bactericidal testing of tigecycline and to investigate its bactericidal activity against clinical isolates of Gram-positive and Gram-negative bacteria. Tigecycline is the first in a new class of glycylcycline antibiotics exhibiting in vitro activity against a broad range of bacteria, including multidrug-resistant organisms. Its bactericidal activity in vitro has not been extensively investigated using multiple test conditions. Five growth media comprising Mueller Hinton broth, Minimum Essential Medium of Eagle, Ham F-12, RPMI 1640 and Iso-Sensitest broth (ISB) with and without surfactant (Tween 80) were investigated in vitro to assess tigecycline bactericidal activity. Clinical isolates of meticillin-resistant Staphylococcus aureus, meticillin-susceptible S. aureus, Escherichia coli, Klebsiella pneumoniae and Enterococcus spp., representing the majority of clinically relevant bacteria, were evaluated for the impact of test conditions on the tigecycline minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), ISB with 0.02% Tween 80 most efficiently demonstrated the bactericidal action of tigecycline when evaluated in 64 well-characterised clinical isolates and was considered as the optimal bactericidal test medium. Using this condition, tigecycline approached 56% bactericidal activity with 3log10 reduction in CFUs at 72h incubation. Bactericidal action increased to 80% of strains when 2log10 reduction was used as the endpoint. Only Enterococcus spp. showed no bactericidal response in this analysis. Tigecycline exhibited a bactericidal effect in vitro against Gram-positive and Gram-negative bacteria. At the tested in vitro conditions, tigecycline MICs were unchanged regardless of the different test media used.

Transcriptome assembly and microarray construction for Enchytraeus crypticus, a model oligochaete to assess stress response mechanisms derived from soil conditions.

BackgroundThe soil worm Enchytraeus crypticus (Oligochaeta) is an ecotoxicology model species that, until now, was without genome or transcriptome sequence information. The present research aims at studying the transcriptome of Enchytraeus crypticus, sampled from multiple test conditions, and the construction of a high-density microarray for functional genomic studies.ResultsOver 1.5 million cDNA sequence reads were obtained representing 645 million nucleotides. After assembly, 27,296 contigs and 87,686 singletons were obtained, from which 44% and 25% are annotated as protein-coding genes, respectively, sharing homology with other animal proteomes. Concerning assembly quality, 84% of the contig sequences contain an open reading frame with a start codon while E. crypticus homologs were identified for 92% of the core eukaryotic genes. Moreover, 65% and 77% of the singletons and contigs without known homologs, respectively, were shown to be transcribed in an independent microarray experiment. An Agilent 180 K microarray platform was designed and validated by hybridizing cDNA from 4 day zinc- exposed E. crypticus to the concentration corresponding to 50% reduction in reproduction after three weeks (EC50). Overall, 70% of all probes signaled expression above background levels (mean signal + 1x standard deviation). More specifically, the probes derived from contigs showed a wider range of average intensities when compared to probes derived from singletons. In total, 522 significantly differentially regulated transcripts were identified upon zinc exposure. Several significantly regulated genes exerted predicted functions (e.g. zinc efflux, zinc transport) associated with zinc stress. Unexpectedly, the microarray data suggest that zinc exposure alters retro transposon activity in the E. crypticus genome.ConclusionAn initial investigation of the E. crypticus transcriptome including an associated microarray platform for future studies proves to be a valuable resource to investigate functional genomics mechanisms of toxicity in soil environments and to annotate a potentially large number of lineage specific genes that are responsive to environmental stress conditions.

Effect of Variable Body Mass on Plantar Foot Pressure and Off-Loading Device Efficacy

An increasing body of evidence has implicated obesity as having a negative effect on the development, treatment, and outcome of lower extremity pathologic entities, including diabetic foot disease. The objective of the present study was to increase the body of knowledge with respect to the effects of obesity on foot function. Specifically, we attempted to (1) describe the relationship between an increasing body mass index (BMI) on plantar foot pressures during gait, and (2) evaluate the efficacy of commonly prescribed off-loading devices with an increasing BMI. A repeated measures design was used to compare the peak plantar foot pressures under multiple test conditions, with the volunteers acting as their own controls. The primary outcome measure was the mean peak plantar pressure in the heel, midfoot, forefoot, and first metatarsal, and the 2 variables were modification of patient weight (from “normal” BMI to “overweight,” “obese,” and “morbidly obese”) and footwear (from an athletic sneaker to a surgical shoe, controlled ankle motion walker, and total contact cast). Statistically significant increases in the peak plantar pressures were observed with increasing volunteer BMI weight class, regardless of the off-loading device used. The present investigation has provided unique and specific data with respect to the changes that occur in the peak plantar pressures with variable BMIs across different anatomic levels and with commonly used off-loading devices. From our results, we have concluded that although the plantar pressures increase with increasing weight, it appears that at least some reduction in pressure can be achieved with an off-loading device, most effectively with the total contact cast, regardless of the patient's BMI.

Multi-image oil-film interferometry skin friction measurements

The benefits of analyzing multiple interferogram images obtained using oil-film interferometry in order to determine wall shear stress are assessed. Both dual- and multi-image analysis approaches are implemented and compared to standard single interferogram approaches. Each of the analysis approaches is derived from the thin oil-film equation. To assess the different implementations, both experimental interferograms and simulated oil films are used. The simulations determine the oil-film height as a function of space and time by solving the thin oil-film equation subject to a known wall shear stress distribution, whereas experimental interferograms were obtained in a turbulent flat plate boundary layer. The results of analyzing these data with the three different analysis approaches suggest that they all work equally well when test conditions are approximately steady. For tunnels with long transients at startup or when multiple test conditions need to be measured in a single run, the multi-image approach is recommended.

Binding actions and scenes in visual long-term memory

How does visual long-term memory store representations of different entities (e.g., objects, actions, and scenes) that are present in the same visual event? Are the different entities stored as an integrated representation in memory, or are they stored separately? To address this question, we asked observers to view a large number of events; in each event, an action was performed within a scene. Afterward, the participants were shown pairs of action-scene sets and indicated which of the two they had seen. When the task required recognizing the individual actions and scenes, performance was high (80%). Conversely, when the task required remembering which actions had occurred within which scenes, performance was significantly lower (59%). We observed this dissociation between memory for individual entities and memory for entity bindings across multiple testing conditions and presentation durations. These experiments indicate that visual long-term memory stores information about actions and information about scenes separately from one another, even when an action and scene were observed together in the same visual event. These findings also highlight an important limitation of human memory: Situations that require remembering actions and scenes as integrated events (e.g., eyewitness testimony) may be particularly vulnerable to memory errors.

Detecting False Positives in Multielement Designs

The authors assessed the extent to which multielement designs produced false positives using continuous duration recording (CDR) and interval recording with 10-s and 1-min interval sizes. Specifically, they created 6,000 graphs with multielement designs that varied in the number of data paths, and the number of data points per data path, using a random number generator. In Experiment 1, the authors visually analyzed the graphs for the occurrence of false positives. Results indicated that graphs depicting only two sessions for each condition (e.g., a control condition plotted with multiple test conditions) produced the highest percentage of false positives for CDR and interval recording with 10-s and 1-min intervals. Conversely, graphs with four or five sessions for each condition produced the lowest percentage of false positives for each method. In Experiment 2, they applied two new rules, which were intended to decrease false positives, to each graph that depicted a false positive in Experiment 1. Results showed that application of new rules decreased false positives to less than 5% for all of the graphs except for those with two data paths and two data points per data path. Implications for brief assessments are discussed.

Extension of Bacillus endospore gas dynamic heating studies to multiple species and test conditions

Shock wave-induced damage to a variety of Bacillus endospore species is studied for a wide range of postshock temperatures and test times in oxidative and non-oxidative gas environments. Bacillus atrophaeus and Bacillus subtilis endospores are nebulized into an aqueous aerosol, loaded into the Stanford aerosol shock tube (SAST) and subjected to shock waves of controlled strength. Endospores experience uniform test temperatures between 500 and 1000 K and pressures ranging from 2 to 7 atm, for either a short test time (∼2·5 ms) or a relatively long test time (∼45 ms). During this process, the bioaerosol is observed using in situ laser absorption and scattering diagnostics. Additionally, shock-treated samples are extracted for ex situ analysis including viability plating and flow cytometry. For short test times, results are consistent with previous studies; all endospore species begin to lose the ability to form colonies when shock-heated to temperatures above 500 K, while significant breakdown in morphology is observed for postshock temperatures above 700 K. Oxidative bath gases did not affect viability losses or morphological breakdown rates. Experiments with extended postshock test time showed increased viability loss with minimal morphological damage for shocks between 600 and 700 K. Genetic differences between B. subtilis and B. atrophaeus endospores do not confer noticeable gains in resistance to shock heating. Oxidative environments do not exacerbate shock-induced damage to endospores. Extended test time experiments reinforce our hypothesis that a temperature/time-dependent inactivation mechanism that does not involve morphological breakdown exists at low-to-moderate postshock temperatures. The methodology and experiments described in this paper extend the study of the interactions of endospores with shock/blast waves to new species and environmental conditions.

Modelling of content-aware indicators for effective determination of shot boundaries in compressed MPEG videos

In this paper, a content-aware approach is proposed to design multiple test conditions for shot cut detection, which are organized into a multiple phase decision tree for abrupt cut detection and a finite state machine for dissolve detection. In comparison with existing approaches, our algorithm is characterized with two categories of content difference indicators and testing. While the first category indicates the content changes that are directly used for shot cut detection, the second category indicates the contexts under which the content change occurs. As a result, indications of frame differences are tested with context awareness to make the detection of shot cuts adaptive to both content and context changes. Evaluations announced by TRECVID 2007 indicate that our proposed algorithm achieved comparable performance to those using machine learning approaches, yet using a simpler feature set and straightforward design strategies. This has validated the effectiveness of modelling of content-aware indicators for decision making, which also provides a good alternative to conventional approaches in this topic.

Hypermnesia and total retrieval time

Recall performance sometimes improves over repeated recall attempts, a phenomenon dubbed hypermnesia. A critical theoretical issue is whether hypermnesia is due to repeated testing per se or increased retrieval time. The present experiments investigated by contrasting five testing conditions. All participants were presented with the same study list followed by either two shorter recall tests or a single longer test. In the multiple test conditions, the tests were either separated by a (filled) 7-minute interval (the multiple-split condition), or presented consecutively, with no break (the multiple-immediate condition). In the single test conditions, the test either began at the start of the recall session, after a (filled) 7-minute delay, or with a 7-minute interruption inserted in the middle. The multiple-split condition produced more reminiscence and hypermnesia than the multiple-immediate condition. More importantly, the multiple-split condition produced greater cumulative recall than any of the other conditions (which did not differ among themselves). That is, single and repeated recall tests of equal total duration are not functionally equivalent.

Test Review: Delis-Kaplan Executive Function System

The Delis-Kaplan Executive Function System (D-KEFS; Delis, Kaplan, & Kramer, 2001) represents the first set of executive tests co-normed on a large and representative national sample designed exclusively for the assessment of executive functions including flexibility of thinking, inhibition, problem solving, planning, impulse control, concept formation, abstract thinking, and creativity. The D-KEFS, composed of nine stand alone tests that can be individually or group administered, provides a standardized assessment of executive functions in children and adults between the ages of 8 and 89. Utilizing a “cognitive-process approach,” the D-KEFS tests allow examiners to systematically generate and evaluate relevant clinical hypotheses on executive functioning of a given examinee by comparing and contrasting performance on multiple testing conditions and using contrast measure scores and error analyses. A review of the administration, scoring and interpretation, test construction, standardization, and technical adequacy indicate that the D-KEFS holds much promise not only as a clinical instrument, but also as a research tool for increasing knowledge of the frontal-lobe functions.

A case study of FEA-based crash sensing system calibration

A case study of using non-linear finite element analyses to aid in calibrating an airbag crash sensing system is presented. Details that are crucial for using a single vehicle model to simulate multiple testing conditions were identified and incorporated in a chosen vehicle model. The vehicle model was then used to simulate a set of no-deployment and all-deployment calibration events. The simulated results were compared with test data to assess the capability of the existing non-linear finite element analysis in aiding sensing system calibration.

Effects of session duration on functional analysis outcomes.

We examined the extent to which variations in session duration affected the outcomes of functional analyses. Forty-six individuals, all diagnosed with mental retardation and referred for assessment and treatment of self-injurious or aggressive behavior, participated in functional analyses, consisting of repeated exposure to multiple test conditions during 15-min sessions. For each set of assessment data, new data sets based on session durations of 10 and 5 min were prepared by deleting data from the last 5 and 10 min, respectively, of each session. Each graph (N = 138) was then reviewed individually by graduate students who had previous experience conducting and interpreting functional analyses, but who were blind to both participant identity and session duration. Interpretations of behavioral function based on the 10- and 5-min data sets were then compared with those based on the 15-min data sets. All of the 10-min data sets yielded interpretations identical to those based on 15-min data sets. Interpretations based on the 5-min and 15-min data sets yielded three discrepancies, all of which were the result of increased response rates toward the latter parts of sessions. These results suggest that the efficiency of assessment might be improved with little or no loss in clarity by simply reducing the duration of assessment sessions.

Autonomic function in panic disorder: cardiorespiratory and plasma catecholamine responsivity to multiple challenges of the autonomic nervous system

Panic disorder has been widely hypothesized to be associated with dysfunction of the autonomic nervous system. In this study, 24 patients with panic disorder and 26 healthy control subjects took part in a broad battery of autonomic function tests, each designed to stress the autonomic nervous system in a particular fashion. Testing consisted of postural challenge, isometric exercise, cold pressor, and Valsalva maneuver. Dependent measures included heart rate, vagal tone, blood pressure, respiratory frequency, end-tidal CO 2 levels, and plasma norepinephrine and epinephrine levels. The testing procedures reliably produced changes in autonomic output in the expected directions, but patients with panic disorder were not found to differ from healthy controls in their cardiorespiratory or plasma catecholaminergic responses. This pattern of normal autonomic responsivity in the patients with panic disorder was evident across multiple test conditions with varying autonomic demand characteristics, thereby supporting the integrity of autonomic regulatory systems in this illness. These data run counter to a simple notion of autonomic dysfunction in panic disorder.

Statistical analysis of Salmonella test data and comparison to results of animal cancer tests

A quantitative framework for the analysis of results of the Salmonella (Ames) test is presented, and the relationship between mutagenesis and carcinogenesis is examined. Color graphics are used for the Salmonella data to describe variability, and trends across multiple chemicals and test conditions. Positivity in the Salmonella test, using statistical criteria to classify results, is compared to positivity in carcinogenesis bioassays for 48 chemicals tested in NCI/NTP-sponsored programs. Sensitivity of the Salmonella test across 5 tester strains was 91% ( 21 23 ), while specificity was only 36% ( 9 25 ). Results were most concordant for TA100 Aroclor-induced rat S9: sensitivity was 87%, specificity 64%. The correlation of mutagenic potency and carcinogenic potency was 0.41 ( p < 0.001) for 80 chemicals, using results from both the general published literature and the NCI/NTP-sponsored programs. After removal of 3 extreme values, the correlation was 0.24 ( p = 0.04).

Recognition learning under multiple channel presentation and testing conditions

The research reported here was conducted while the author was a member of the staff of the Division of Academic Research and Services of the Pennsylvania State University under a grant from the Television Bureau of Advertising of New York. Mr. Hartman wishes to acknowledge the contributions of John Hundleby of the Division's staff who read the manuscript in its entirety and made many helpful comments. Acknowledgment is also given to Dr. C. R. Carpenter and Mr. Leslie P. Greenhill, director and associate director, respectively, of the Division for their support and encouragement. Mr. Hartman is currently a member of the faculty of Dickinson College, Carlisle, Pennsylvania.