Lack Of Repeatability Research Articles

Behavioral variation post-invasion: Resemblance in some, but not all, behavioral patterns among invasive and native praying mantids

Animal invasions can be devastating for native species. Behavioral variation is known to influence animal invasions, yet comparatively less is known about how behavioral variation influences invasive-native species interactions. Here we examined how the mean and variance surrounding several behavioral traits in two sympatric species of praying mantis differ and how these behavioral types translate to actual prey capture success using the introduced European mantis, Mantis religiosa, and the native bordered mantis, Stagmomantis limbata. We assayed time spent in the open (risk proneness), response towards a novel prey, and voracity within a population of M. religiosa and S. limbata. We found that the native and invasive mantids displayed no differences in their average behavioral tendencies. The native exhibited significant levels of repeatability in voracity while the invasive did not. The lack of repeatability in the invasive appears to be driven by lower levels of among-individual variation in voracity. This may have evolutionary consequences for native S. limbata if it results in strong selection in native levels of mean and among-individual variation. Significant levels of among-individual differences were found in other behaviors (response to a novel prey and risk proneness) across species, suggesting less selection on invasive behavioral variation in these traits. Risk proneness and response towards a novel prey also formed a behavioral syndrome across species, yet neither behavior was correlated with voracity in either species. Our results illustrate the need to examine the ecological effects of behavioral variation of both invasive and native species to determine how that might impact invasive-native interactions.

Quantitative optical coherence tomography angiography of the peripapillary circulation in glaucoma.

The cause of glaucoma, a disease defined by degeneration of retinal ganglion cells associated with cupping of the optic nerve head (ONH) and progressive vision loss, continues to be debated despite numerous advances in ophthalmic imaging and diagnostics. Although elevated intraocular pressure is often implicated, many studies, using a variety of imaging techniques including plain fundus photography, fluorescein angiography, laser Doppler flowmetry, and color Doppler ultrasound (1-4), have suggested that insufficiencies of ONH circulation may play a role in glaucoma pathogenesis. While all of these imaging modalities have been informative, each has a set of limitations, including low spatial resolution, invasiveness, restriction to superficial vessels, lack of repeatability, and modality specific artifacts. Optical coherence tomography angiography (OCTA), an imaging technology that can produce high resolution, three-dimensional images of fundus microcirculation, is well suited to overcome many of these limitations (5).

Linear motor driven double inverted pendulum: A novel mechanical design as a testbed for control algorithms

The inverted pendulum is a classic experimental facility that is widely used as a benchmark for testing control algorithms. One of the difficulties, however, with the traditional inverted pendulum is that it is not a very challenging problem to compare modern control techniques. In addition, it is usually driven by a rotary motor and transmission system that introduces mechanical friction forces as well as periodic and aperiodic disturbances which result in the pendulum performance not as repeatable as desired. In particular, this lack of repeatability, which is very difficult to model, makes the use of this traditional control testbed less desirable for developing and comparing various modern control techniques. Therefore, it is the purpose of this paper to describe a more repeatable but more complicated inverted pendulum system as a benchmark system for testing control strategies. The proposed system includes the use of a linear drive motor to eliminate the difficulties associated with the rotary transmission. In addition, a second inverted pendulum is added to create a richer control space and thus be a more effective benchmark for controller evaluation.

Boldness: are open field and startle tests measuring the same personality trait?

Boldness, the willingness of individuals to engage in risky behaviour, is one of the most studied personality traits. It has been measured using a variety of tests; however, measuring a behaviour using different assays may lead to a jingle fallacy. The few studies that have attempted to determine whether these different assays are comparable have produced mixed results. A lack of repeatability between boldness measures under standardized and natural conditions may be the source of this variation. Here, we tested whether risk-taking behaviour of free-living African striped mice, Rhabdomys pumilio, measured in a laboratory using open field tests is comparable with measures of risk-taking behaviour from startle tests. These measures were then compared with measures of risk-taking behaviour obtained from equivalent open field and startle tests performed on the same individuals under natural conditions. During open field tests, we assessed the time an individual spent away from the wall of the arena (in the laboratory) or from its nest (in nature). During startle tests, we measured the latency to re-emerge from either a protective box (in the laboratory) or a nest (under natural conditions) after an individual was scared away. Our results showed that risk-taking behaviour measured using the open field and the startle tests were repeatable within the same context (tested twice per assay) and across contexts (laboratory, nature). However, open field measures of risk-taking behaviour were not correlated with startle measures, supporting the idea that the two tests are assaying different personality traits. The variations in the outcome observed in the two assays probably resulted from the presentation of threatening stimuli in the startle test. We propose that, at least in striped mice, the startle test is more suitable for measuring anxiety than boldness.

Modified WIC test: an efficient and effective tool for evaluating pipeline girth weldability

ABSTRACTThe Welding Institute of Canada (WIC) test is a simple and standardised weldability test for hydrogen assisted cold cracking that was developed in the 80s. It has been extensively utilised by the industry to qualify safe welding envelopes but the difficult access to the weldment by instrumentation hinders its use for scientific research. Moreover the lack of repeatability arising from the traditional manual deposit and the short weld length causes industrial trials to have a low success rate. The present work proposes a modified geometry, referred to as the modified WIC (MWIC) test that shows: (1) an improved success rate of weld deposition, (2) an enhancement to instrument the weldment and (3) welding conditions in better accordance with the field pipeline girth welding conditions. The design is validated under a mechanised, shielded metal arc welding process with the cellulosic electrodes used for in-field pipeline construction.

The potential of iRest in measuring the hand function performance of stroke patients.

Clinical scales such as Fugl-Meyer Assessment (FMA) and Motor Assessment Scale (MAS) are widely used to evaluate stroke patient's motor performance. However, there are several limitations with these assessment scales such as subjectivity, lack of repeatability, time-consuming and highly depend on the ability of the physiotherapy. In contrast, robot-based assessments are objective, repeatable, and could potentially reduce the assessment time. However, robot-based assessments are not as well established as conventional assessment scale and the correlation to conventional assessment scale is unclear. This study was carried out to identify important parameters in designing tasks that efficiently assess hand function of stroke patients and to quantify potential benefits of robotic assessment modules to predict the conventional assessment score with iRest. Twelve predictive variables were explored, relating to movement time, velocity, strategy, accuracy and smoothness from three robotic assessment modules which are Draw I, Draw Diamond and Draw Circle. Regression models using up to four predictors were developed to describe the MAS. Results show that the time given should be not too long and it would affect the trajectory error. Besides, result also shows that it is possible to use iRest in predicting MAS score. There is a potential of using iRest, a non-motorized device in predicting MAS score.

Reliability and repeatability of testing visual evoked potential habituation in migraine: A blinded case-control study.

Background Many studies have shown that migraine patients have an interictal habituation deficit of visual evoked potentials (VEPs). Some discordant results were attributed to non-blinded analyses and a lack of repeatability. Aims In this study, we compared blinded and non-blinded analyses of the same recordings and assessed test-retest repeatability. Methods VEP recordings of 25 healthy volunteers (HVs) and 78 episodic migraine patients (EMs; 52 interictal, 26 ictal) were analysed by two investigators, one of whom was blinded to diagnosis and headache phase. Twelve HVs and nine EMs had two recordings for test repeatability. Results In both blinded and non-blinded analyses, VEP habituation was normal in HVs and EMs during an attack, but deficient in EMs interictally. Intra-individual habituation percentages were highly correlated in two recordings separated by ≥7 days. Conclusions The studies showing a VEP habituation deficit in migraineurs between attacks are unlikely to be biased by non-blinding analysis or poor repeatability.

Robotic Assessment Modules for Upper Limb Stroke Assessment: Preliminary Study

Conventional assessment scales are widely used to quantify motor performance in stroke survivors. Although they are widely used, there are several limitations with these assessment scales such as lack of repeatability, subjective, time-consuming and it depends on the ability of the trained physiotherapist. In contrast, robot-based assessments are highly repeatable, objective, and could potentially reduce assessment time. However, robotbased assessments are not as well established as conventional assessment scale and the correlation to conventional assessment scale is unclear. This study was to determine if there are any similarities in the movements between the proposed robotic assessment modules namely as Draw Square, Draw Diamond and Draw Circle and between the sequences, clockwise and counter clockwise on 10 male healthy subjects. Result shows that there are no similarities between each robotic assessment modules and between the sequences. All kinematic variables extracted from each robotic assessment modules can be used as benchmark for assessment purpose in stroke patient.

Influence of rotor position on the repeatability of frequency response analysis measurements on rotating machines and a statistical approach for more meaningful diagnostics

This work presents an investigation on the influence of rotor position on the Frequency Response Analysis (FRA) of electric machines. Different types of machines have been analyzed. Contrary to common belief, not only the salient-pole machine suffered from rotor position influence on the FRA. This can have severe impact on the repeatability of the tests and, consequently, their ability to identify early damage in the insulation system of the machine. This paper is intended to warn practitioners of FRA that care should be taken while analyzing the results, in order to avoid false positives in their measurements. Recommendations are made aiming to avoid the influence of rotor position on the results. Also, the use of statistical techniques is proposed, in order to improve the diagnosis, even when there is some lack of repeatability.

A fragmented adeno-associated viral dual vector strategy for treatment of diseases caused by mutations in large genes leads to expression of hybrid transcripts.

Dual vector AAV systems are being utilised to enable gene therapy for disorders in which the disease gene is too large to fit into a single capsid. Fragmented adeno-associated viral (fAAV) vectors containing single inverted terminal repeat truncated transgenes have been considered as one such gene replacement strategy. Here we aim to add to the current understanding of the molecular mechanisms employed by fAAV dual vector systems. Oversized (>8kb) transgene constructs containing ABCA4 coding sequence were packaged as truncated fragments <5kb in size into various AAV serotypes. In vitro transductions with these fAAV vector preparations were conducted with mRNA and protein expression products assessed by way of RT-PCR, qPCR and western blot techniques. Transductions with fAAV vector preparations yielded ABCA4 mRNA, but did not generate detectable levels of protein. Sequencing of the transcript population revealed the presence of full length ABCA4 CDS with additional hybrid ABCA4 variants, indicating truncated transgenes without regions of overlap were joining and forming stable hybrid transgenes. In contrast, an ABCA4 overlapping dual vector system (OV) with a defined complementary region generated only full length mRNA transcripts plus detectable ABCA4 protein. Despite previous success shown with the fAAV approach, the lack of repeatability and identification of stable hybrid transcripts capable of protein production suggests there is more refinement required before considering this approach in a clinical setting.

Novel Method for Calculating a Nonsubjective Informative Prior for a Bayesian Model in Toxicology Screening: A Theoretical Framework.

In toxicology screening (forensic, food-safety), due to several analytical errors (e.g., retention time shift, lack of repeatability in m/z scans, etc.), the ability to confidently identify/confirm a compound remains a challenge. Due to these uncertainties, a probabilistic approach is currently preferred. However, if a probabilistic approach is followed, the only statistical method that is capable of estimating the probability of whether the compound of interest (COI) is present/absent in a given sample is Bayesian statistics. Bayes' theorem can combine prior information (prior probability) with data (likelihood) to give an optimal probability (posterior probability) reflecting the presence/absence of the COI. In this work, a novel method for calculating an informative prior probability for a Bayesian model in targeted toxicology screening is introduced. In contrast to earlier proposals making use of literature citation rates and the prior knowledge of the analyst, this method presents a thorough and nonsubjective approach. The formulation approaches the probability calculation as a clustering and random draw problem that incorporates few analytical method parameters meticulously estimated to reflect sensitivity and specificity of the system. The practicality of the method has been demonstrated and validated using real data and simulated analytical techniques.

내부 최적화를 이용한 화학 센서의 단기 드리프트 분석 및 보정

One of the main problems when working the chemical sensor is the lack of repeatability and reproducibility of the sensor response. If the problem is not properly taken into consideration, the stability and reliability of the system using chemical sensors would be decreased. In this paper we analyzed the sensor's drift of short term and proposed a compensation method for reducing the effects of the drift in order to improve the stability and the reliability of the chemical sensor. The sensor drift was analyzed by a trend line graph and CV(coefficient of variation) was used to quantify. And we compensated for the drift by using the internal normalization. As a result it was found that the value of CV was decreased after compensation.

Feature extraction and early warning of agglomeration in fluidized bed reactors based on an acoustic approach

The potential use of audible acoustic emissions for monitoring particle agglomeration in ethylene polymerization fluidized bed reactors was investigated by the authors and reported in this paper. The offset in the power spectral centroid between normal and agglomeration signals was compared, and the energy distribution of the acoustic signals was confirmed to change under agglomeration conditions. On this basis, the acoustic signals were decomposed by wavelet packet decomposition (WPD) and the energy ratios of every sub-band were set as the voiceprint. Subsequently, principal component analysis (PCA) was introduced to reduce the dimensionality of the feature vector. Furthermore, based on normal signals, an agglomeration warning model could be created by support vector data description (SVDD) to avoid the decrease in description accuracy caused by the lack of agglomeration samples. Finally, a proper alarm rate (AR) parameter was designed to solve the problem of false alarms caused by the lack of repeatability and haphazardness of agglomeration in polymerization. According to the experimental results in a pilot plant, the proposed early-warning approach for agglomeration could provide a warning 20–50min in advance of the traditional pressure and temperature monitoring methods.

Repeatability of Octadecyl Methacrylate-Based Monolithic Columns for Capillary Electrochromatography

Octadecyl methacrylate-based monolithic capillary columns were prepared using octadecyl methacrylate as the monomer, ethylene dimethacrylate as the cross-linking agent, 2-acryloylamido-2-methylpropanesulfonic acid as the ionizable monomer, responsible for a negatively charged stationary phase surface and able to support a cathodic electrosmotic flow, and amyl alcohol and 1,4-butanediol as porogenic solvents. The repeatability of the morphological aspect of the monolithic material was evaluated by scanning electron microscopy (SEM). The uniformity along the same monolithic bed was also investigated by SEM. Replicate determinations of surface area and pore volume were also performed and compared. The repeatability of the obtained electrochromatographic efficiencies for separations of alkylbenzenes using the stationary phases prepared was also evaluated. A column that had a plate height of 31 μm was tested for separation of polycyclic aromatic hydrocarbons. Even though minimal possible variation of experimental parameters was maintained, it was not possible to reproduce the stationary phases of the monolithic columns, since the relative standard deviation for the efficiencies obtained on columns prepared from the same polymerization mixture composition was 62%. The lack of repeatability for the efficiency is thought to be a result of limited homogeneity of the monolithic globular structures along the length of the majority of the prepared columns. The poor precision of preparation was justified by the copolymerization reaction that occurs in the presence of 2, 2′-azobisisobutyronitrile as the initiator agent, whose decomposition starts at the moment that this is added to the reaction mixture.

Laser forming systems: a review

Laser forming plastically deforms the material by means of a laser beam with or without the application of mechanical loads. It can be used for bending of sheets and tubes and also for producing complex shapes. Laser shock forming deforms the material with a high power laser pulse. The laser forming is highly suitable for rapid prototyping and forming of materials with poor workability. A number of researchers studied the process and suggested the strategies for process design, control and optimisation. There is still a need for developing accurate mathematical models and optimisation strategies for enhancing the effectiveness and applicability of the process. The edge effect, occasional melting in the irradiated region, changes in material properties, lack of repeatability in bend angle and difficulty in online monitoring are the major challenging issues needed to be circumvented for making the process popular in industry.

The Time Dependent Solvent Extraction of Ta and Nb

The suitability of Liquid-liquid extraction (LLE) for the selective extraction of chemically similar tantalum (Ta) and niobium (Nb) mixtures was investigated by determining the influence of the acid concentration, extractant to metal mole ratio (E:M) as well as the ageing of the feed on extraction using the extractants, bis (2-ethylhexyl) phosphate (D2EHPA) and di-iso-octylphosphinic acid (PA). The system consisted of a solvent in varying E:M ratio’s, diluted in cyclohexane with 3% (v\v) 1-octanol added as modifier and a feed solution containing sulphuric acid and 100 ppm of the NH4TaF6and NH4NbF6complexes. Depending on the acid concentration, extraction percentages (%E) of up to 100% for Ta and 10-20% for Nb were attained. An initial lack of repeatability in experimental results was shown to be caused by variations in the age of the feed solution. The change in extraction trends expressed as a normalized %E for the aged feed solutions were nearly identical for both extractants when using 3, 6, 9 and 14mol/dm3H2SO4. For the 3 and 6mol/dm3solutions, the %E decreased significantly within the first 4-5 hours of ageing. At 9mol/dm3the %E remained stable for feed ages up to 3.5 hours before declining, while the %E remained near constant at 14mol/dm3even after ageing for 24 hours.

Characterising lower limb muscle activity and test-retest repeatability of EMG measures in healthy adults during upright pedalling

Background: Upright pedalling (UP) has similarities to walking in terms of both muscle activation and biomechanical activity. Therefore, UP is a potential rehabilitation therapy for enhancing walking recovery. The development of UP as a rehabilitation intervention requires understanding of muscle activity patterns elicited during pedalling in a range of participants, including young healthy adults. The aims of this study were: to characterise muscle activation patterns during UP in young healthy adults, and to investigate the test-retest repeatability of EMG-derived measures used to characterise activity patterns. Methods: Participants (total n=8, females: n=7) performed two UP sessions, separated by a 1-hour rest period. During UP, muscle activity of rectus femoris (RF) and biceps femoris (BF) was recorded using surface EMG. Lower limb muscle activity was characterised by average, integrated activity (iEMG) for each muscle group according to four 90° phases of the 360° wheel turn. This procedure provided a measure of muscle activity throughout the pedalling cycle. Testretest repeatability of mean iEMG values for each pedal revolution was calculated using an intraclass correlation coefficient (ICC) with 95% confidence intervals (CI). Results: Characterisation of activity: muscle activity for all participants during UP demonstrated reciprocal muscle activation of BF and RF. More specifically, RF exhibited double bursts of activity at 0–135° and 270–360°, whereas BF demonstrated a single burst at 135–270°. Test-retest repeatability: appeared high for RF when considering the point estimate (ICC=0.837), but the associated wide CIs (-0.224–1.39) mean that this finding is imprecise. A lack of repeatability observed for BF (ICC=0.02) was also inconclusive due to wide CI's (-0.258–0.737). Conclusions: UP elicited a reciprocal muscle activation pattern in RF and BF in a small sample of young healthy volunteers. Definitive test-retest repeatability of recorded measures was not established. Implications: This study has contributed normative data on muscle activation patterns during walking-like activity, and data to inform sample size for definitively testing intra-participant variance.

Passive Upper Limb Assessment Device

Stroke is the leading cause of disability. Reaching movement is the most important movement for many daily activities routine. Rehabilitation is to encourage and enhanced recovery process. Conventional rehabilitation is one-to-one intervention where labour intensive and lack of repeatability. In addition, the stroke assessments by physiotherapist are subjective and not independent. Thus, this paper will describe the design and development of non-motorized system for assessing the patients’ motor function. This system will be used in the future to find the correlation between conventional assessments scales such Fugl-Mayer Assessment (FMA), Chedoke-McMaster Stroke Assessment Scale (CMSA) and Motor Assessment Scale (MAS) and robotic assessment.

Comparative analysis of optimisation methods applied to thermal cycle of a coal fired power plant

Abstract The paper presents a thermodynamic optimization of 900MW power unit for ultra-supercritical parameters, modified according to AD700 concept. The aim of the study was to verify two optimisation methods, i.e., the finding the minimum of a constrained nonlinear multivariable function (fmincon) and the Nelder-Mead method with their own constrain functions. The analysis was carried out using IPSEpro software combined with MATLAB, where gross power generation efficiency was chosen as the objective function. In comparison with the Nelder-Mead method it was shown that using fmincon function gives reasonable results and a significant reduction of computational time. Unfortunately, with the increased number of decision parameters, the benefit measured by the increase in efficiency is becoming smaller. An important drawback of fmincon method is also a lack of repeatability by using different starting points. The obtained results led to the conclusion, that the Nelder-Mead method is a better tool for optimisation of thermal cycles with a high degree of complexity like the coal-fired power unit.

Genomic mechanisms accounting for the adaptation to parasitism in nematode-trapping fungi.

Orbiliomycetes is one of the earliest diverging branches of the filamentous ascomycetes. The class contains nematode-trapping fungi that form unique infection structures, called traps, to capture and kill free-living nematodes. The traps have evolved differently along several lineages and include adhesive traps (knobs, nets or branches) and constricting rings. We show, by genome sequencing of the knob-forming species Monacrosporium haptotylum and comparison with the net-forming species Arthrobotrys oligospora, that two genomic mechanisms are likely to have been important for the adaptation to parasitism in these fungi. Firstly, the expansion of protein domain families and the large number of species-specific genes indicated that gene duplication followed by functional diversification had a major role in the evolution of the nematode-trapping fungi. Gene expression indicated that many of these genes are important for pathogenicity. Secondly, gene expression of orthologs between the two fungi during infection indicated that differential regulation was an important mechanism for the evolution of parasitism in nematode-trapping fungi. Many of the highly expressed and highly upregulated M. haptotylum transcripts during the early stages of nematode infection were species-specific and encoded small secreted proteins (SSPs) that were affected by repeat-induced point mutations (RIP). An active RIP mechanism was revealed by lack of repeats, dinucleotide bias in repeats and genes, low proportion of recent gene duplicates, and reduction of recent gene family expansions. The high expression and rapid divergence of SSPs indicate a striking similarity in the infection mechanisms of nematode-trapping fungi and plant and insect pathogens from the crown groups of the filamentous ascomycetes (Pezizomycotina). The patterns of gene family expansions in the nematode-trapping fungi were more similar to plant pathogens than to insect and animal pathogens. The observation of RIP activity in the Orbiliomycetes suggested that this mechanism was present early in the evolution of the filamentous ascomycetes.