Short-term Repeatability Research Articles

Period doubling behavior in human steady state visual evoked potentials

Objective. Previous human steady state visual evoked potential (SSVEP) experiments have yielded different results regarding the range of stimulus frequencies in which period doubling (PD) behavior is observed. This study aims at obtaining experimental and statistical data regarding the frequency range of PD generation and also investigates other characteristics of PD. Approach. In two sets of experiments, seven subjects were presented a sinusoidal flickering light stimulus with frequencies varying from 15 to 42 Hz. To observe the short term variations in PD generation, another set of 5 successive experiments were performed on five subjects with 10 min breaks in between. To obtain the SSVEP responses, filtering, signal averaging and power spectral density (PSD) estimation were applied to the recorded electroencephalogram. From the PSD estimates, subharmonic occurrence rates were calculated for each experiment and were used along with ANOVA for interpreting the outcomes of the short term repeatability experiments. Main results. Although fundamental (excitation frequency) and second harmonic components appear in almost all SSVEP spectra, there is considerable inter-subject and intra-subject variability regarding PD occurrence. PD occurs for all stimulus frequencies from 15 to 42 Hz when all subjects are considered together. Furthermore, the statistical analyses of short term repeatability experiments suggest that in the short term, PD generation is consistent when all frequencies are considered together but for a single frequency significant short term differences occur. There also is considerable variation in the ratio of subharmonic amplitude to fundamental amplitude across different frequencies for a given subject. Significance. Important results and statistical data are obtained regarding PD generation. Our results indicate that modeling studies should attempt to generate PD for a broader range of stimulus frequencies. It is argued that SSVEP based brain–computer interface applications would likely benefit from the utilization of subharmonics in classification.

Between-occasion repeatability of fractional exhaled nitric oxide measurements in children.

ABSTRACTThe aim of the study was to assess short-term repeatability of measurements of fractional exhaled nitric oxide (FENO) and its correlates in children in the 6- to 9-year age bracket participating in a respiratory epidemiological survey. FENO was measured in two sessions one week apart in 101 children. Participants were divided into three groups: asymptomatic (n = 76); symptomatic (n = 14); and asthma (n = 11). Absolute and relative differences between the measurements, as well as concordance correlation coefficients, were used in order to assess repeatability. The two FENO measurements were strongly correlated (0.98). Although intragroup comparisons of the two measurements were not significantly different (p = 0.2), intergroup comparisons were. FENO measurements are reproducible in children in epidemiological settings.

Short-term repeatability of non-invasive aortic pulse wave velocity measures

ObjectiveTo compare the short-term repeatability of aortic pulse wave velocity (PWV) measures obtained with non-invasive devices.MethodsIn 102 patients planned to undertake a cardiac catheterization (65 ± 13 years, 70.6% males) duplicate non-invasive measures of PWV, 15-mi-nutes apart, were obtained with 4 devices measuring two-points carotid-femoral PWV and the related pulse transit time (PTT): Complior (AlamMed-ical), PulsePenETT, PulsePenET (DiaTecne), SphygmoCor (AtCorMedical), and with 2 devices estimating PWV from the oscillometric cuff-derived brachial wave: BPLab (Petr Telegin), Mobil-O-Graph (IEM). PWV and carotid-femoral PTT measurements were compared using coefficients of variation (CV%) and their confidence intervals (CI).ResultsDevices evaluating carotid-femoral PWV showed a good repeatability (CV%[CI]: Complior: 8.8 [7.3–10.1]; PulsePen ETT: 8.0 [6.2–9.5]; Pul-sePen ET: 5.8 [4.9–6.6]; SphygmoCor: 9.5 [7.7–11.0]), whereas the repeatability of PWV estimated by cuff-based devices was for the BPLab = 5.5 [4.2–6.6] and for the Mobil-O- Graph = 3.4 [2.9–3.8]). A tendency toward a lower repeatability of carotid-femoral PWV was present for greater arterial stiffness, while repeatability of carotid-femoral PTT was not related to its mean values. Differences between repeated PWV measurements were not correlated with blood pressure (R2 = 0.005) or heart rate variations (R2 = 0.013).ConclusionsShort-term repeatability of PWV measures was good, with some differences between different devices. A greater repeatability was observed in devices estimating PTT from a cuff-based measurement, compared to devices measuring carotid-femoral PTT, owing to the algorithm of calculation of PWV (Mobil-O-Graph) or to the procedure of correction which eliminates highly variable PWV values (BPLab).Repeatability of PWV is not influenced by blood pressure or heart rate variations. For carotid-femoral PWV, the repeatability of measures is lower for higher PWV values.

Impedance Spectroscopy of Aqueous Solution Samples of Different Glucose Concentrations for the Exploration of Non-Invasive-Continuous-Blood-Glucose-Monitoring

Continuous blood-glucose-monitoring provides maximal information about the fluctuations of blood-glucose levels throughout the day and thus plays a vital role in controlling the blood-glucose level in diabetes. The conventional methods of testing blood-glucose level are invasive, painful and are unsuitable for continuous monitoring. Thus, the battle for developing bloodless and painless blood-glucose monitors has begun from past three decades. Electrical bio-impedance spectroscopy has been suggested as one of the potential technique for the development of such monitors. The present work is aimed at impedance spectroscopy to demonstrate the variation in electrical bio-impedance properties of blood with the change in glucose concentration. Glucose-dependent electrical impedance parameters of aqueous solution samples, of increasing glucose concentration have been determined to accomplish the same. The glucose-dependent capacitance and conductance illustrates the direct variations in impedance parameters with respect to change in glucose concentration. Measurement automation program is developed to ease the measurement procedure, to support continuous measurement, and to compute short-term repeatability of measurement results. The experimental results of the present work will be used to implement electrical bio-impedance spectroscopy technique in the development of non-invasive-continuous-blood-glucose monitoring system.

A high performance humidity sensor based on surface acoustic wave and graphene oxide on AlN/Si layered structure

A surface acoustic wave (SAW) humidity sensor based on AlN/Si (doped) layered structure and graphene oxide (GO) sensing layer is proposed for high sensitivity and low temperature coefficient of frequency. With the GO thin film, the sensitivity of the humidity sensor is increased to 42.08 kHz/RH% when the relative humidity is greater than 80%RH. The humidity sensor performs well even at both very low (≤10%RH) and very high (≥90%RH) detection range of humidity. The present sensor has low hysteresis, excellent short term repeatability and long term stability (variation less than ± 2%). The sensor also shows a fast response and short recovery time. Moreover, using the AlN/Si (doped) layered structure, the thermal stability of the sensor is significantly improved. After being covered with GO thin film, the temperature coefficient of frequency (TCF) of the sensor is further reduced to −22.1 ppm/°C, much smaller than the previously reported SAW humidity sensors.

Repeatability of the infant food reinforcement paradigm: Implications of individual and developmental differences

The relative reinforcing value of food versus engagement in other behaviors may be related to the development of obesity, and interventions to reduce FRR may prevent the development of obesity. Our laboratory recently developed a paradigm to measure the reinforcing value of food versus an alternative behavior (i.e., playing with bubbles) in infants using a computerized laboratory task, during which infants press a button to earn reinforcers following a progressive ratio schedule of reinforcement. The primary purpose of this study was to examine the short-term (within 2 weeks) repeatability of this measure, specifically the outcome of infant food reinforcing ratio (FRR), or how hard infants will work for food relative to the alternative. The secondary aim was to examine whether infant age and temperament dimensions related to novelty responsiveness (high intensity pleasure and approach) moderated the repeatability of FRR. Thirty-seven infants aged 9–18 months completed this study. Repeated measures analysis of variance (ANOVA) showed no differences between time 1 and time 2 in responding for food (F = 0.463, p = 0.501), bubbles (F = 1.793, p = 0.189), or overall FRR (F = 0.797, p = 0.378). Regression models showed the association between BUB Pmax at time 1 and time 2 were moderated by infant age (p = 0.04), with greater repeatability in older infants. Linear regression models also demonstrated that the infant temperamental dimension of high intensity pleasure significantly predicted BUB Pmax at time 1 (β = 2.89, p = 0.01), but not at time 2. Overall, our findings support the repeatability of this measure for food portion of the reinforcement task, but demonstrated that the measure of non-food portion of the task required modification, in particular among children younger than 13 months old.

Repeatability of apparent diffusion coefficient and intravoxel incoherent motion parameters at 3.0 Tesla in orbital lesions

ObjectivesTo evaluate repeatability of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) parameters in the orbit.MethodsFrom December 2015 to March 2016, 22 patients were scanned twice using an IVIM sequence with 15b values (0–2,000 s/mm2) at 3.0T. Two readers independently delineated regions of interest in an orbital mass and in different intra-orbital and extra-orbital structures. Short-term test-retest repeatability and inter-observer agreement were assessed using the intra-class correlation coefficient (ICC), the coefficient of variation (CV) and Bland-Altman limits of agreements (BA-LA).ResultsTest-retest repeatability of IVIM parameters in the orbital mass was satisfactory for ADC and D (mean CV 12% and 14%, ICC 95% and 93%), poor for f and D*(means CV 43% and 110%, ICC 90% and 65%). Inter-observer repeatability agreement was almost perfect in the orbital mass for all the IVIM parameters (ICC = 95%, 93%, 94% and 90% for ADC, D, f and D*, respectively).ConclusionsIVIM appeared to be a robust tool to measure D in orbital lesions with good repeatability, but this approach showed a poor repeatability of f and D*.Key Points• IVIM technique is feasible in the orbit.• IVIM has a good–acceptable repeatability of D (CV range 12–25 %).• IVIM interobserver repeatability agreement is excellent (ICC range 90–95 %).• f or D* provide higher test-retest and interobserver variabilities.

Performance of a fast and high-resolution multi-echo spin-echo sequence for prostate T2 mapping across multiple systems.

To evaluate the performance of a multi-echo spin-echo sequence with k-t undersampling scheme (k-t T2 ) in prostate cancer. Phantom experiments were performed at five systems to estimate the bias, short-term repeatability, and reproducibility across all systems expressed with the within-subject coefficient of variation (wCV). Monthly measurements were performed on two systems for long-term repeatability estimation. To evaluate clinical repeatability, two T2 maps (voxel size 0.8 × 0.8 × 3 mm3 ; 5 min) were acquired at separate visits on one system for 13 prostate cancer patients. Repeatability was assessed per patient in relation to spatial resolution. T2 values were compared for tumor, peripheral zone, and transition zone. Phantom measurements showed a small bias (median = -0.9 ms) and good short-term repeatability (median wCV = 0.5%). Long-term repeatability was 0.9 and 1.1% and reproducibility between systems was 1.7%. The median bias observed in patients was -1.1 ms. At voxel level, the median wCV was 15%, dropping to 4% for structures of 0.5 cm3 . The median tumor T2 values (79 ms) were significantly lower (P < 0.001) than in the peripheral zone (149 ms), but overlapped with the transition zone (91 ms). Reproducible T2 mapping of the prostate is feasible with good spatial resolution in a clinically reasonable scan time, allowing reliable measurement of T2 in structures as small as 0.5 cm3 . Magn Reson Med 79:1586-1594, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Magnetic resonance elastography of the pancreas: Measurement reproducibility and relationship with age

PurposeTo determine magnetic resonance elastography (MRE)-derived stiffness of pancreas in healthy volunteers with emphasis on: 1) short term and midterm repeatability; and 2) variance as a function of age. MethodsPancreatic MRE was performed on 22 healthy volunteers (age range:20–64years) in a 3T–scanner. For evaluation of reproducibility of stiffness estimates, the scans were repeated per volunteer on the same day (short term) and one month apart (midterm). MRE wave images were analyzed using 3D inversion to estimate the stiffness of overall pancreas and different anatomic regions (i.e., head, neck, body, and tail). Concordance and Spearman correlation tests were performed to determine reproducibility of stiffness measurements and relationship to age. ResultsA strong concordance correlation (ρc=0.99; p-value<0.001) was found between short term and midterm repeatability pancreatic stiffness measurements. Additionally, the pancreatic stiffness significantly increased with age with good Spearman correlation coefficient (all ρ>0.81; p<0.001). The older age group (>45yrs) had significantly higher stiffness compared to the younger group (≤45yrs) (p<0.001). No significant difference (p>0.05) in stiffness measurements was observed between different anatomical regions of pancreas, except neck stiffness was slightly lower (p<0.012) compared to head and overall pancreas at month 1. ConclusionMRE-derived pancreatic stiffness measurements are highly reproducible in the short and midterm and increase linearly with age in healthy volunteers. Further studies are needed to examine these effects in patients with various pancreatic diseases to understand potential clinical applications.

Characterisation of a plastic scintillation detector to be used in a multicentre stereotactic radiosurgery dosimetry audit

Scintillation detectors are considered highly suitable for dosimetric measurement of small fields in radiotherapy due to their near-tissue equivalence and their small size. A commercially available scintillation detector, the Exradin W1 (Standard Imaging, Middleton, USA), has been previously characterised by two independent studies (Beierholm et al., 2014; Carrasco et al., 2015a, 2015b) but the results from these publications differed in some aspects (e.g. energy dependence, long term stability). The respective authors highlighted the need for more studies to be published (Beierholm et al., 2015; Carrasco et al., 2015a, 2015b).In this work, the Exradin W1 was characterised in terms of dose response, dependence on dose rate, energy, temperature and angle of irradiation, and long-term stability. The observed dose linearity, short-term repeatability and temperature dependence were in good agreement with previously published data. Appropriate corrections should therefore be applied, where possible, in order to achieve measurements with low-uncertainty. The angular dependence was characterised along both the symmetrical and polar axis of the detector for the first time in this work and a dose variation of up to 1% was observed. The response of the detector was observed to decrease at a rate of approximately 1.6%kGy−1 for the first 5kGy delivered, and then stabilised to 0.2%kGy−1 in the subsequent 20kGy.The main goal of this work was to assess the suitability of the Exradin W1 for use in dose verification measurements for stereotactic radiosurgery. The results obtained confirm that the detector is suitable for use in such situations. The detector is now utilised in a multi-centre stereotactic radiosurgery dosimetric audit, with the application of appropriate correction factors.

Test-retest repeatability of patterns of brain activation provoked by bladder filling.

To assess short-term repeatability of an fMRI protocol widely used to assess brain control of the bladder. fMRI offers the potential to discern incontinence phenotypes as well as the mechanisms mediating therapeutic response. If so, this could enable more targeted efforts to enhance therapy. Such data, however, require excellent test-retest repeatability. Fifty-nine older women (age ≥60 years) with urgency incontinence underwent two fMRI scans within 5-10 min with a concurrent bladder infusion/withdrawal protocol. Activity in three brain regions relevant to bladder control was compared using paired t tests and intra-class correlation. There were no statistically significant differences in brain activity between the two consecutive scans in the regions of interest. Intra-class correlation was 0.19 in the right insula, 0.32 in the dorsal anterior cingulate cortex/supplementary motor area, and 0.44 in the medial pre-frontal cortex. Such correlations are considered fair or poor, but are comparable to those from studies of other repeated fMRI tasks. This is the first evaluation of the repeatability of a bladder fMRI protocol. The technique used provides a framework for comparing different fMRI protocols applied to brain-bladder research. Despite universal patient response to the stimulus, brain response had limited repeatability within individuals. Improvement of the investigational protocol should magnify brain response and reduce variability. These results suggest that although analysis of fMRI data among groups of subjects yields valuable insight into bladder control, fMRI is not yet appropriate for evaluation of the brain's role in continence on an individual level.

Macular pigment optical density: repeatability, intereye correlation, and effect of ocular dominance.

PurposeTo evaluate short-term repeatability, intereye correlation, and effect of ocular dominance on macular pigment optical density (MPOD) measurements obtained using the QuantifEye Heterochromatic Flicker Photometer.Patients and methodsA total of 72 study participants were enrolled in this prospective, cross-sectional study. Participants underwent a comprehensive ocular evaluation, including visual acuity, evaluation of ocular dominance, slit lamp examination, intraocular pressure measurement, and optic nerve head and macula analysis using optical coherence tomography and fundus photography. All study participants after initial training underwent MPOD measurement twice in both eyes in a randomized sequence. The repeatability was tested using Altman and Bland plots for first measurements with the second measurements for right eye and left eye and additionally by grouping eyes as a function of ocular dominance. The Pearson correlation coefficient was performed to assess the intereye correlation of MPOD values.ResultsThe mean age of study participants was 35.5 years (range 22–68 years). The mean MPOD measurements for OD (right eye) and OS (left eye) were 0.47 and 0.48, respectively, which followed a normal distribution (Shapiro–Wilk test, P=0.6 and 0.2). The 95% limits of agreement of Altman and Bland plots for the first and second measurements were −0.12 to +0.11 and −0.13 to +0.12 for OD and OS, respectively. The correlation coefficient of mean MPOD measurements of OD and OS was r statistic =0.94 (Pearson correlation coefficient P<0.0001; r2 0.89). The 95% limits of agreement of Altman and Bland plots when evaluated by laterality of eye or by ocular dominance were narrow, with limits of agreement ranging from −0.13 to +0.12.ConclusionThe MPOD measurements obtained using the QuantifEye show good short-term repeatability. There is excellent intereye correlation, indicating that the MPOD values of one eye data can predict the fellow eye value with 89% accuracy. The ocular dominance had no bearing on the outcome of this psychophysical test in ocular healthy eyes.

Determination of Glucose-Dependent Dielectric Properties of Ringer Lactate Using Open-Ended Coaxial Probe Method

The reported work is the basis of exploration of non-invasive-continuous-blood-glucose monitoring technique using electrical bioimpedance spectroscopy method. This requires the determination of variation in dielectric properties of blood as a function of glucose. The present paper attempts to discuss the findings of in-vitro experiment performed in this direction. The experiment was performed to analyze the variations in dielectric properties of equivalent physiological solution as a function of glucose concentration over a frequency range from 100 MHz to 2.5 GHz. The glucose-dependent dielectric constant of ringer lactate samples prepared with different concentrations of d-glucose ranging from 100 to 500 mg/dL has been determined by employing open-ended coaxial probe method. The short-term repeatability of dielectric constant of DI water at a particular temperature found to be good. The real part of the dielectric constant of RL decreases with increase in glucose concentration along with frequency.

Short-Term Repeatability of Stabilometric Assessments

ABSTRACTThe authors evaluated the short-term (within-day, between-days) repeatability of center of pressure (COP) displacements. COP sway area and speed were obtained in the morning and afternoon of two separate days, both with open (EO) and closed (EC) eyes, in 10 healthy adults. Agreement and variability among conditions were tested by ANOVA and Bland-Altman plots. Mode (EO/EC, area: p = .032; speed: p < .004), and day (day1/day2, area: p = .006; speed: p = .02) showed significant differences. The EC condition and the second test day showed the largest values, with medium-large effect sizes. Time-of-day did not influence COP displacements. Speed had better agreement than area (Bland-Altman plots). COP displacements were well reproducible within-day, but had significant between-days variations. COP assessments should be performed in the same session.

Development of a temperature-controlled phantom for magnetic resonance quality assurance of diffusion, dynamic, and relaxometry measurements.

Diffusion-weighted (DW) and dynamic contrast-enhanced magnetic resonance imaging (MRI) are increasingly applied for the assessment of functional tissue biomarkers for diagnosis, lesion characterization, or for monitoring of treatment response. However, these techniques are vulnerable to the influence of various factors, so there is a necessity for a standardized MR quality assurance procedure utilizing a phantom to facilitate the reliable estimation of repeatability of these quantitative biomarkers arising from technical factors (e.g., B1 variation) affecting acquisition on scanners of different vendors and field strengths. The purpose of this study is to present a novel phantom designed for use in quality assurance for multicenter trials, and the associated repeatability measurements of functional and quantitative imaging protocols across different MR vendors and field strengths. A cylindrical acrylic phantom was manufactured containing 7 vials of polyvinylpyrrolidone (PVP) solutions of different concentrations, ranging from 0% (distilled water) to 25% w/w, to create a range of different MR contrast parameters. Temperature control was achieved by equilibration with ice-water. Repeated MR imaging measurements of the phantom were performed on four clinical scanners (two at 1.5 T, two at 3.0 T; two vendors) using the same scanning protocol to assess the long-term and short-term repeatability. The scanning protocol consisted of DW measurements, inversion recovery (IR) T1 measurements, multiecho T2 measurement, and dynamic T1-weighted sequence allowing multiple variable flip angle (VFA) estimation of T1 values over time. For each measurement, the corresponding calculated parameter maps were produced. On each calculated map, regions of interest (ROIs) were drawn within each vial and the median value of these voxels was assessed. For the dynamic data, the autocorrelation function and their variance were calculated; for the assessment of the repeatability, the coefficients of variation (CoV) were calculated. For both field strengths across the available vendors, the apparent diffusion coefficient (ADC) at 0 °C ranged from (1.12 ± 0.01) × 10(-3) mm(2)/s for pure water to (0.48 ± 0.02) × 10(-3) mm(2)/s for the 25% w/w PVP concentration, presenting a minor variability between the vendors and the field strengths. T2 and IR-T1 relaxation time results demonstrated variability between the field strengths and the vendors across the different acquisitions. Moreover, the T1 values derived from the VFA method exhibited a large variation compared with the IR-T1 values across all the scanners for all repeated measurements, although the calculation of the standard deviation of the VFA-T1 estimate across each ROI and the autocorrelation showed a stability of the signal for three scanners, with autocorrelation of the signal over the dynamic series revealing a periodic variation in one scanner. Finally, the ADC, the T2, and the IR-T1 values exhibited an excellent repeatability across the scanners, whereas for the dynamic data, the CoVs were higher. The combination of a novel PVP phantom, with multiple compartments to give a physiologically relevant range of ADC and T1 values, together with ice-water as a temperature-controlled medium, allows reliable quality assurance measurements that can be used to measure agreement between MRI scanners, critical in multicenter functional and quantitative imaging studies.

Short term repeatability of body fat thickness measurement and body condition scoring in sheep as assessed by a relatively small number of assessors

This study evaluated the intra-observer repeatability of the rump fat thickness (RFT) measurements by ultrasound and body condition scoring (BCS) in sheep, and the reproducibility of RFT and BCS determined i) by six investigators, ii) at different sites (left and right, lumbar and sternal) and iii) in unshorn and shorn sheep. Six investigators with different experience in estimating body condition score in sheep determined BCS and RFT repeatedly at the different sites in 65 ewes before and after shearing. Intra-observer repeatability was greater for repeated measurement of RFT left (r=0.83 and r=0.84, in unshorn and shorn sheep) than RFT right (r=0.64 and r=0.77, resp.). A lower repeatability for measuring the sternal fat thickness (SFT) in unshorn sheep (r=0.31) indicates that this method is not feasible to score ewes. The correlation between fat thicknesses determined at different sites (RFT left, RFT right, SFT) and in unshorn and shorn sheep revealed a generally higher reproducibility of RFT measurements left and right (r=0.63–0.76) compared with the reproducibility of RFT and SFT (r=0.37–0.79). Repeatability and reproducibility varied between investigators and in unshorn and shorn sheep. The repeatability for measuring BCS lumbar in unshorn and shorn sheep was greater (κ=0.73 and κ=0.67, resp.) than for determining BCS sternal (κ=0.01 and κ=0.44, resp.) and varied between investigators and in unshorn and shorn ewes. Reproducibility of lumbar and sternal BSC determined by the six investigators was poor to fair in unshorn and poor to moderate in shorn ewes. In summary, measuring RFT or BCS at a sternal site cannot be recommended. Furthermore, taking measurement on shorn seep improved reproducibility. Based on these results, the assessment of RFT or BCS in sheep has the greatest repeatability in the lumbar region. It has to be noted that this study analyzed the repeatability but not the accuracy of the described methods.

Do personalities co-vary with metabolic expenditure and glucocorticoid stress response in adult lizards?

Stable differences in physiology among individuals may facilitate the evolution of consistent individual differences in behavior. In particular, according to the pace-of-life syndrome (POLS) hypothesis, individual variation in metabolic expenditure and stress physiology should be linked with exploration, aggression, or risk taking behaviors. Previous studies have uncovered stable individual differences in metabolic expenditure and circulating glucorticoids in common lizards (Zootoca vivipara). We tested for correlations between standard metabolic rates (SMR), glucorticoid stress response and behavioral traits (activity, aggressiveness, risk taking and sociability) in males. In ectotherms, the thermal dependence of SMR should be included in the POLS hypothesis; we therefore measured SMR at three temperatures from rest to preferred body temperature. Activity, aggressiveness and risk taking, but not sociability, exhibited significant, short term repeatability, and little correlation was found between behavioral traits. The SMR of lizards with a low metabolism at rest increased faster with body temperature. The SMR at rest was negatively correlated with behavioral variation in sociability and activity but not with risk taking behavior. In addition, the plasma corticosterone level after an acute, handling stress increased slightly but not significantly with aggressiveness. We discuss alternative interpretations for these relationships and conclude that the link between inter-individual variation in physiology and behavior is trait-dependent in the common lizard.

Comparison of nitrous oxide (N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O) analyzers for high-precision measurements of atmospheric mole fractions

Abstract. Over the last few decades, in situ measurements of atmospheric N2O mole fractions have been performed using gas chromatographs (GCs) equipped with electron capture detectors. This technique, however, becomes very challenging when trying to detect the small variations of N2O as the detectors are highly nonlinear and the GCs at remote stations require a considerable amount of maintenance by qualified technicians to maintain good short-term and long-term repeatability. With new robust optical spectrometers now available for N2O measurements, we aim to identify a robust and stable analyzer that can be integrated into atmospheric monitoring networks, such as the Integrated Carbon Observation System (ICOS). In this study, we present the most complete comparison of N2O analyzers, with seven analyzers that were developed and commercialized by five different companies. Each instrument was characterized during a time period of approximately 8 weeks. The test protocols included the characterization of the short-term and long-term repeatability, drift, temperature dependence, linearity and sensitivity to water vapor. During the test period, ambient air measurements were compared under field conditions at the Gif-sur-Yvette station. All of the analyzers showed a standard deviation better than 0.1 ppb for the 10 min averages. Some analyzers would benefit from improvements in temperature stability to reduce the instrument drift, which could then help in reducing the frequency of calibrations. For most instruments, the water vapor correction algorithms applied by companies are not sufficient for high-precision atmospheric measurements, which results in the need to dry the ambient air prior to analysis.

Recent social conditions affect boldness repeatability in individual sticklebacks

Animal personalities are ubiquitous across the animal kingdom and have been shown both to influence individual behaviour in the social context and to be affected by it. However, little attention has been paid to possible carryover effects of social conditions on personality expression, especially when individuals are alone. Here we investigated how the recent social context affected the boldness and repeatability of three-spined sticklebacks, Gasterosteus aculeatus, during individual assays. We housed fish either solitarily, solitarily part of the time or socially in groups of four, and subjected them twice to a risk-taking task. The social conditions had a large effect on boldness repeatability, with fish housed solitarily before the trials showing much higher behavioural repeatability than fish housed socially, for which repeatability was not significant. Social conditions also had a temporal effect on the boldness of the fish, with only fish housed solitarily taking more risks during the first than the second trial. These results show that recent social conditions can thus affect the short-term repeatability of behaviour and obfuscate the expression of personality even in later contexts when individuals are alone. This finding highlights the need to consider social housing conditions when designing personality studies and emphasizes the important link between animal personality and the social context by showing the potential role of social carryover effects.

Combined uncertainty estimation for the determination of the dissolved iron amount content in seawater using flow injection with chemiluminescence detection.

This work assesses the components contributing to the combined uncertainty budget associated with the measurement of the Fe amount content by flow injection chemiluminescence (FI‐CL) in <0.2 μm filtered and acidified seawater samples. Amounts of loaded standard solutions and samples were determined gravimetrically by differential weighing. Up to 5% variations in the loaded masses were observed during measurements, in contradiction to the usual assumptions made when operating under constant loading time conditions. Hence signal intensities (V) were normalised to the loaded mass and plots of average normalised intensities (in V kg−1) vs. values of the Fe amount content (in nmol kg−1) added to a “low level” iron seawater matrix were used to produce the calibration graphs. The measurement procedure implemented and the uncertainty estimation process developed were validated from the agreement obtained with consensus values for three SAFe and GEOTRACES reference materials (D2, GS, and GD). Relative expanded uncertainties for peak height and peak area based results were estimated to be around 12% and 10% (coverage factor k = 2), respectively. The most important contributory factors were the uncertainty on the sensitivity coefficient (i.e., calibration slope) and the within‐sequence‐stability (i.e., the signal stability over several hours of operation; here 32 h). For GD, using peak height measurements, these factors contributed respectively 69.7% and 21.6% while the short‐term repeatability accounted for only 7.9%. Therefore, an uncertainty estimation based on the intensity repeatability alone, as is often done in FI‐CL studies, is not a realistic estimation of the overall uncertainty of the procedure.