Significant Systematic Biases Research Articles

Optimizing wearable single-channel EEG sleep staging in a heterogeneous sleep-disordered population using transfer learning.

While various wearable EEG devices have been developed, performance evaluation of the devices and their associated automated sleep stage classification models is mostly limited to healthy subjects. A major barrier for applying automated wearable EEG sleep staging in clinical populations is the need for large-scale data for model training. We therefore investigated transfer learning as strategy to overcome limited data availability and optimize automated single-channel EEG sleep staging in people with sleep disorders. We acquired 52 single-channel frontopolar headband EEG recordings from a heterogeneous sleep-disordered population with concurrent PSG. We compared three model training strategies: 'pre-training' (i.e., training on a larger dataset of 901 conventional PSGs), 'training-from-scratch' (i.e., training on wearable headband recordings), and 'fine-tuning' (i.e., training on conventional PSGs, followed by training on headband recordings). Performance was evaluated on all headband recordings using 10-fold cross-validation. Highest performance for 5-stage classification was achieved with fine-tuning (κ = .778), significantly higher than with pre-training (κ = .769) and with training-from-scratch (κ = .733). No significant differences or systematic biases were observed with clinically relevant sleep parameters derived from PSG. All sleep disorder categories showed comparable performance. This study emphasizes the importance of leveraging larger available datasets through deep transfer learning to optimize performance with limited data availability. Findings indicate strong similarity in data characteristics between conventional PSG and headband recordings. Altogether, results suggest the combination of the headband, classification model, and training methodology can be viable for sleep monitoring in the heterogeneous clinical population.

Assessment of the reliability, responsiveness, and meaningfulness of the scale for the assessment and rating of ataxia (SARA) for lysosomal storage disorders.

To evaluate the reliability, responsiveness, and validity of theScale for the Assessment and Rating of Ataxia (SARA) in patients with lysosomal storage disorders (LSDs) who present with neurological symptoms, and quantify the threshold for a clinically meaningful change. We analyzed data from three clinical trial cohorts (IB1001-201, IB1001-202, and IB1001-301) of patients with Niemann-Pick disease type C (NPC) and GM2 Gangliosidoses (Tay-Sachs and Sandhoff disease) comprising 122 patients and 703 visits. Reproducibility was described as re-test reliability between repeat baseline visits or baseline and post-treatment washout visits. Responsiveness was determined in relation to the Investigator's, Caregiver's, and Patient's Clinical Global Impression of Improvement (CGI-I). The CGI-I data was also used to quantify a threshold for a clinically meaningful improvement on the SARA scale. Using a qualitative methods approach, patient/caregiver interviews from the IB1001-301 trial were further used to assess a threshold of meaningful change as well as the breadth of neurological signs and symptoms captured and evaluated by the SARA scale. The Inter-Class Correlation (ICC) was 0.95 or greater for all three trials, indicating a high internal consistency/reliability. The mean change in SARA between repeat baseline and post-treatment washout visit assessments in all trials was -0.05, SD 1.98, i.e., minimal, indicating no significant differences, learning effects or other systematic biases. For the CGI-I responses and change in SARA scores, Area Under the Curve (AUC) values were 0.82, 0.71, and 0.77 for the Investigator's, Caregiver's, and Patient's CGI-I respectively, indicating strong agreement. Further qualitative analyses of the patient/caregiver interviews demonstrated a 1-point or greater change on SARA to be a clinically meaningful improvement which is directly relevant to the patient's everyday functioning and quality of life. Changes captured by the SARA were also paralleled by improvement in a broad range of neurological signs and symptoms and beyond cerebellar ataxia. Qualitative and quantitative data demonstrate the reliability and responsiveness of the SARA score as a valid measure of neurological signs and symptoms in LSDs with CNS involvement, such as NPC and GM2 Gangliosidoses. A 1-point change represents a clinically meaningful transition reflecting the gain or loss of complex function.

Comparison of Inter-Method Agreement and Reliability for Automatic Brain Volumetry Using Three Different Clinically Available Software Packages.

Background and Objectives: No comparative study has evaluated the inter-method agreement and reliability between Heuron AD and other clinically available brain volumetric software packages. Hence, we aimed to investigate the inter-method agreement and reliability of three clinically available brain volumetric software packages: FreeSurfer (FS), NeuroQuant® (NQ), and Heuron AD (HAD). Materials and Methods: In this study, we retrospectively included 78 patients who underwent conventional three-dimensional (3D) T1-weighed imaging (T1WI) to evaluate their memory impairment, including 21 with normal objective cognitive function, 24 with mild cognitive impairment, and 33 with Alzheimer's disease (AD). All 3D T1WI scans were analyzed using three different volumetric software packages. Repeated-measures analysis of variance, intraclass correlation coefficient, effect size measurements, and Bland-Altman analysis were used to evaluate the inter-method agreement and reliability. Results: The measured volumes demonstrated substantial to almost perfect agreement for most brain regions bilaterally, except for the bilateral globi pallidi. However, the volumes measured using the three software packages showed significant mean differences for most brain regions, with consistent systematic biases and wide limits of agreement in the Bland-Altman analyses. The pallidum showed the largest effect size in the comparisons between NQ and FS (5.20-6.93) and between NQ and HAD (2.01-6.17), while the cortical gray matter showed the largest effect size in the comparisons between FS and HAD (0.79-1.91). These differences and variations between the software packages were also observed in the subset analyses of 45 patients without AD and 33 patients with AD. Conclusions: Despite their favorable reliability, the software-based brain volume measurements showed significant differences and systematic biases in most regions. Thus, these volumetric measurements should be interpreted based on the type of volumetric software used, particularly for smaller structures. Moreover, users should consider the replaceability-related limitations when using these packages in real-world practice.

Performance Evaluation of LMI Based on Low-Frequency Three-Dimensional Total Lightning Flash Location Data

At present, there is still some uncertainty in the evaluation of the performance of the Fengyun 4A Lightning Mapping Imager (LMI), which is mainly limited by the detection performance of the reference detection system and the suitability of the evaluation method. In this paper, a one-to-one performance evaluation of the LMI was performed based on total lightning flash data from the lightning Low-Frequency Electric field Detection Array (LFEDA). It was found that there were significant systematic biases in the discharge results detected via LMI, with a median of −0.946 s, −0.0817°, and −0.0245° in time bias, longitude bias, and latitude bias, respectively. The evaluation results after removing the systematic biases indicated that the relative detection efficiency for flashes of LMI was 17.6%, the mean and median time errors were both 0.647 s, and the mean and median distance errors were 6.09 km and 5.02 km, respectively. The relative detection efficiency for groups of LMI was 9.8%, the mean and median time errors were 0.674 s and 0.660 s, and the mean and median distance errors were 7.19 km and 6.54 km, respectively. The detection efficiency of LMI for both flashes and groups at nighttime was significantly higher than its detection efficiency during the daytime. The relative detection efficiency for flashes of LMI at nighttime was 26.5%, while during the daytime it was 14.4%. The relative detection efficiency for groups of LMI at nighttime was 16.2%, while during the daytime it was only 7.4%. The spatial accuracy for both flashes and groups was always better during the daytime than at nighttime.

Establishment of a corrective geoid surface by spline approximation of Iranian GNSS/levelling network

The performance of the gravimetric geoid models is usually evaluated by comparison of geoid heights with the GNSS/levelling derived geoid. But the GNSS/levelling network can be infected by significant systematic biases and random errors, especially in large and uneven areas. This contribution addresses the challenging problem of the corrector surface development along with the elimination of biases. To this end, fitting an appropriate geometric surface to the GNSS/levelling geoid heights is required, which is accomplished by applying the least squares B-spline approximation theory to the GNSS/levelling data. In addition, the 3D affine transformation is used to detect systematic effects of the GNSS/levelling network compared to a global geoid model. This strategy is applied to the adjustment of the Iranian GNSS/levelling network. A significant tilt is observed across the country ranging from −0.35 m to 0.04 m. The entire study area is divided into four zones and the corrector surfaces are obtained in each zone. The accuracy of three global geoid models, EGM2008, EIGEN-6C4 and SGG-UGM-1, along with that of the Iranian regional geoid model IRG2016, are then investigated based on the raw GNSS/levelling heights and the corrector surfaces. The evaluations show the reliable results regarding the corrector surfaces against the raw data set. All geoid models show their maximum RMSE values of discrepancies in the mountainous zones and their minimum RMSEs in the zones having lower variety in topography. This indicates that the irregular topographies are not well detected by the global models over the study area.

Automated Brain Volumetry in Patients With Memory Impairment: Comparison of Conventional and Ultrafast 3D T1-Weighted MRI Sequences Using Two Software Packages.

BACKGROUND. Isotropic 3D T1-weighted imaging has long acquisition times, potentially leading to motion artifact and altered brain volume measurements. Acquisition times may be greatly shortened using an isotropic ultrafast 3D echo-planar imaging (EPI) T1-weighted sequence. OBJECTIVE. The purpose of this article was to compare automated brain volume measurements between conventional 3D T1-weighted imaging and ultrafast 3D EPI T1-weighted imaging. METHODS. This retrospective study included 36 patients (25 women, 11 men; mean age, 68.4 years) with memory impairment who underwent 3-T brain MRI. Examinations included both conventional 3D T1-weighted imaging using inversion recovery gradient-recalled echo sequence (section thickness, 1.0 mm; acquisition time, 3 minutes 4 seconds) and, in patients exhibiting motion, an isotropic ultrafast 3D EPI T1-weighted sequence (section thickness, 1.2 mm; acquisition time, 30 seconds). The 36-patient sample excluded five patients in whom severe motion artifact rendered the conventional sequence of insufficient quality for volume measurements. Automated brain volumetry was performed using NeuroQuant (version 3.0, CorTechs Laboratories) and FreeSurfer (version 7.1.1, Harvard University) software. Volume measurements were compared between sequences for nine regions in each hemisphere. RESULTS. Volumes showed substantial to almost perfect agreement between the two sequences for most regions bilaterally. However, most regions showed significant mean differences between sequences, and Bland-Altman analyses showed consistent systematic biases and wide limits of agreement (LOA). For example, for the left hemisphere using NeuroQuant, volume was significantly greater for the ultrafast sequence in four regions and significantly greater for the conventional sequence in three regions, whereas standardized effect size between sequences was moderate for four regions and large for one region. Using NeuroQuant, mean bias (ultrafast minus conventional) and 95% LOA were greatest in cortical gray matter bilaterally (-50.61 cm3 [-56.27 cm3, -44.94 cm3] for the left hemisphere; -50.02 cm3 [-54.88 cm3, -45.16 cm3] for the right hemisphere). The variation between the two sequences was observed in subset analyses of 16 patients with and 20 patients without Alzheimer disease. CONCLUSION. Brain volume measurements show significant differences and systematic biases between the conventional and ultrafast sequences. CLINICAL IMPACT. In patients in whom severe motion artifact precludes use of the conventional sequence, the ultrafast sequence may be useful to enable brain volume-try. However, the current conventional 3D T1-weighted sequence remains preferred in patients who can tolerate the standard examination.

Accuracy and Error Trends of Commercially Available Bat Swing Sensors in Baseball.

In baseball, the swing speed and swing angle of the bat just before ball impact are important to increase the speed and horizontal distance of a batted ball. This study investigated the accuracies and error trends of four commercially available bat sensors to measure these parameters. The hitting motions of seven healthy participants were measured simultaneously using the bat sensors and an optical motion capture system, and the swing speeds and swing angles were compared. The swing speed was measured with high accuracy, as indicated by the high intraclass correlation coefficient (ICC) between the bat sensor and the motion capture system measurements (mean ICC = 0.78). However, the ICC for the swing angle was lower (mean ICC = 0.58) than that of the swing speed for all but one bat sensor, indicating low accuracy. Moreover, in the high swing speed range, the accuracy of the swing speed tended to decrease for three bat sensors, but the trend of the swing angle was different among bat sensors. Significant systematic biases or proportional errors were found for all bat sensors, indicating the possibility of error correction. The sensor used in this study can help to evaluate the differences between players with different competition levels and hitting motions. Coaches need to be cautious in taking measurements of players with high swing speeds and in assessing slight changes within an individual.

Reliability Of Isokinetic Knee Flexion And Extension Total Work And Unilateral Endurance Ratios

PURPOSE: Isokinetic assessment of unilateral knee flexor and extensor functionality is often evaluated through the hamstrings-quadriceps (H:Q) strength ratio, measured in units of peak torque. Clinical use of an isokinetic unilateral H:Q endurance ratio, measured in units of total work, may provide a supplementary perspective of knee flexor and extensor functionality, yet the reliability of this measure has not yet been established. Therefore, the purpose of this study was to determine the intersession reliability of knee flexion (KF) and extension (KE) total work, and the unilateral H:Q endurance ratio. METHODS: Twenty-eight healthy young adults (14 males, 14 females) volunteered for two isokinetic (60°/s, 6 repetitions) testing sessions (48 hr apart). Dominant (DOM) and nondominant (NDOM) KF and KE testing was conducted in a random limb testing order; KE and KF total work was computed across the 6 repetitions, as well as the unilateral H:Q endurance ratio (KF ÷ KE). Following normality and heteroscedasticity exploration, relative reliability of the total work measures was assessed by interclass correlation coefficients (ICC, model: 2,1) while dependent t tests were used to evaluate systematic bias between the two testing sessions. Additionally, absolute reliability was assessed by calculating coefficients of variation (CV). RESULTS: ICCs were excellent for KF and KE of both limbs, ranging from .892 to .911, with NDOM extension being the lowest (95% confidence interval: .780-.949). The unilateral H:Q endurance ratio displayed good relative reliability for the DOM (.709) and NDOM (.719) limbs. No significant systematic biases were noted for any KF and KE total work, or unilateral H:Q endurance ratio measures (P ≥ .167) and all CVs for KF and KF were below 15%, ranging from 7.89% (DOM, KE) to 13.1% (NDOM, KF). Lastly, unilateral H:Q endurance ratios CVs for both limbs were below 10% (DOM, 9.08%; NDOM, 8.66%). CONCLUSION: These results demonstrate that DOM and NDOM KF and KE total work and unilateral H:Q endurance ratios have acceptable intersession reliability in healthy young adults. Future work will examine clinical utilization of isokinetic unilateral H:Q endurance ratios, in addition to H:Q strength ratios, to gain a more comprehensive isokinetic evaluation of patient KF and KE functionality.

Evaluation of techniques used to assess skeletal muscle quantity in patients with cirrhosis.

Loss of skeletal muscle mass is a well-recognised complication of cirrhosis. Bedside methods to assess skeletal muscle mass including anthropometrics and bioelectrical impedance analysis (BIA) are negatively impacted by fluid overload in advanced cirrhosis and thus there is a need to identify alternatives. There is a paucity of data on the accuracy of commonly used radiological methods such as dual X-ray absorptiometry (DXA) to assess appendicular lean mass (ALM), and computed tomography (CT) skeletal muscle area in patients with cirrhosis. The aim of this study was to evaluate the relationships and agreement of several skeletal muscle mass estimation methods compared to a reference model in patients with cirrhosis. A cross-sectional, single centre study was performed by prospectively recruiting patients with cirrhosis referred to the Queensland Liver Transplant Service. Patients underwent assessment of skeletal muscle mass using bedside techniques (mid-upper arm muscle circumference (MUAMC), bioelectrical impedance spectroscopy (BIS), ultrasound muscle thickness (USMT)) and radiological methods (DXA ALM, CT skeletal muscle area). These were compared to a reference measurement of body cell mass derived from a multi-compartment model using isotope dilution tests and DXA. Forty-two patients (age 56 years, interquartile range 48-60, 86% male) were recruited. Bedside skeletal muscle mass estimation techniques were strongly correlated to the body cell mass reference, with BIS estimation having the strongest correlation coefficients (r=0.78-0.79; P<0.01). A novel technique measuring USMT offered no advantage over traditional bedside techniques. Of the radiological methods, DXA ALM had the strongest correlation coefficient (r=0.781; P<0.01). Weaker correlation coefficients were observed in patients with ascites, except when using the MUAMC. Bland-Altman analysis of BIS body composition estimates demonstrated significant systematic biases and large limits of agreement compared to reference values. These results confirm the difficulties in assessing skeletal muscle mass in patients with cirrhosis, particularly in those with ascites. DXA ALM and BIS measurements provided the best correlation to body cell mass. We suggest DXA ALM for estimation of skeletal muscle mass in patients with cirrhosis as there are established thresholds for skeletal muscle mass depletion, and an accurate assessment of bone mass and density can also be provided. The use of USMT over other bedside skeletal muscle mass estimates was not supported by our results. Further studies evaluating novel bedside skeletal muscle mass estimation techniques in cirrhosis patients are required.

Inter-Device Agreement between Fitbit Flex 1 and 2 for Assessing Sedentary Behavior and Physical Activity.

This study examined the inter-model agreement between the Fitbit Flex (FF) and FF2 in estimating sedentary behavior (SED) and physical activity (PA) during a free-living condition. 33 healthy adults wore the FF and FF2 on non-dominant wrist for 14 consecutive days. After excluding sleep and non-wear time, data from the FF and FF2 was converted to the time spent (min/day) in SED and PA using a proprietary algorithm. Pearson’s correlation was used to evaluate the association between the estimates from FF and FF2. Mean absolute percent errors (MAPE) were used to examine differences and measurement agreement in SED and PA estimates between FF and FF2. Bland-Altman (BA) plots were used to examine systematic bias between two devices. Equivalence testing was conducted to examine the equivalence between the FF and FF2. The FF2 had strong correlations with the FF in estimating SED and PA times. Compared to the FF, the FF2 yielded similar SED and PA estimates along with relatively low measurement discords and did not have significant systematic biases for SED and Moderate-to-vigorous PA estimates. Our findings suggest that researchers may choose FF2 as a measurement of SED and PA when FF is not available in the market during the longitudinal PA research.

Comparison of PR, QRS, and QT interval measurements by seven ECG interpretation programs

BackgroundElectrocardiograph-generated measurements of PR, QRS, and QT intervals are generally thought to be more precise than manual measurements on paper records. However, the performance of different programs has not been well compared. MethodsRoutinely obtained digital electrocardiograms (ECGs), including over 500 pediatric ECGs, were used to create over 2000 10 s analog ECGs that were replayed through seven commercially available electrocardiographs. The measurements for PR interval, QRS duration, and QT interval made by each program were extracted and compared against each other (using the median of the programs after correction for program bias) and the population mean values. ResultsSmall but significant systematic biases were seen between programs. The smallest and largest variation from the population mean differed by 4.7 ms for PR intervals, 5.8 ms for QRS duration, and 12.4 ms for QT intervals. In pairwise comparison programs showed similar accuracy for most ECGs, with the average absolute errors at the 75th percentile for PR intervals being 4–6 ms from the median, QRS duration 4–8 ms, and QT interval 6–10 ms. However, substantial differences were present in the numbers and extent of large, clinically significant errors (e.g at the 98th percentile), for which programs differed by a factor of two for absolute errors, as well as differences in the mix of overestimations and underestimations. ConclusionsWhen reading digital ECGs, users should be aware that small systematic differences exist between programs and that there may be large clinically important errors in difficult cases.

Beware of commonly used approximations. Part II. Estimating systematic biases in the best-fit parameters

Cosmological parameter estimation from forthcoming experiments promise to reach much greater precision than current constraints. As statistical errors shrink, the required control over systematic errors increases. Therefore, models or approximations that were sufficiently accurate so far, may introduce significant systematic biases in the parameter best-fit values and jeopardize the robustness of cosmological analyses. We generalize previously proposed expressions to estimate a priori the systematic error introduced in parameter inference due to the use of insufficiently good approximations in the computation of the observable of interest or the assumption of an incorrect underlying model. Although this methodology can be applied to measurements of any scientific field, we illustrate its power by studying the effect of modeling the angular galaxy power spectrum incorrectly. We also introduce Multi_CLASS, a new, public modification of the Boltzmann code CLASS, which includes the possibility to compute angular cross-power spectra for two different tracers. We find that significant biases in most of the cosmological parameters are introduced if one assumes the Limber approximation or neglects lensing magnification in modern galaxy survey analyses, and the effect is in general larger for the multi-tracer case, especially for the parameter controlling primordial non-Gaussianity of the local type, fNL.

Observational constraints on the origin of the elements

Manganese (Mn) is a key Fe-group element, commonly employed in stellar population and nucleosynthesis studies to explore the role of SN Ia. We have developed a new non-local thermodynamic equilibrium (NLTE) model of Mn, including new photo-ionisation cross-sections and new transition rates caused by collisions with H and H− atoms. We applied the model in combination with one-dimensional (1D) LTE model atmospheres and 3D hydrodynamical simulations of stellar convection to quantify the impact of NLTE and convection on the line formation. We show that the effects of NLTE are present in Mn I and, to a lesser degree, in Mn II lines, and these increase with metallicity and with the effective temperature of a model. Employing 3D NLTE radiative transfer, we derive a new abundance of Mn in the Sun, A(Mn) = 5.52 ± 0.03 dex, consistent with the element abundance in C I meteorites. We also applied our methods to the analysis of three metal-poor benchmark stars. We find that 3D NLTE abundances are significantly higher than 1D LTE. For dwarfs, the differences between 1D NLTE and 3D NLTE abundances are typically within 0.15 dex, however, the effects are much larger in the atmospheres of giants owing to their more vigorous convection. We show that 3D NLTE successfully solves the ionisation and excitation balance for the RGB star HD 122563 that cannot be achieved by 1D LTE or 1D NLTE modelling. For HD 84937 and HD 140283, the ionisation balance is satisfied, however, the resonance Mn I triplet lines still show somewhat lower abundances compared to the high-excitation lines. Our results for the benchmark stars confirm that 1D LTE modelling leads to significant systematic biases in Mn abundances across the full wavelength range from the blue to the IR. We also produce a list of Mn lines that are not significantly biased by 3D and can be reliably, within the 0.1 dex uncertainty, modelled in 1D NLTE.

Systematic ultrastructural comparison of swept-source and full-depth spectral domain optical coherence tomography imaging of diabetic macular oedema

Background/AimsOptical coherence tomography (OCT) is commonly used to diagnose and assess diabetic macular oedema (DME). Swept-source OCT (SS-OCT) promises improved imaging depth and more independence from media opacities. Heidelberg Spectralis...

Comparison of Forced and Impulse Oscillometry Measurements: A Clinical Population and Printed Airway Model Study

The use of commercialised forced oscillation (FOT) devices to assess impedance in obstructive diseases such as asthma has gained popularity. However, it has yet to be fully established whether resistance and reactance measurements are comparable across different FOT devices, particularly in disease. We compared two commercially available FOT devices: Impulse Oscillometry (IOS) and TremoFlo FOT (Thorasys) in a) clinical adult population of healthy controls (n = 14), asymptomatic smokers (n = 17) and individuals with asthma (n = 73) and b) a 3D printed CT-derived airway tree model resistance, as well as a 3 L standardised volume reactance. Bland-Altman Plots and linear regressions were used to evaluate bias between the devices. Resistance measurements at both 5 and 20 Hz were numerically higher with IOS compared to FOT, with evidence of small and statistically significant proportional systematic bias and a positive Bland-Altman regression slope at both 5 and 20 Hz. In contrast, the IOS device recorded reactances that were less negative at both 5 Hz and 20 Hz and significantly smaller reactance areas when compared to TremoFlo. Larger statistically significant proportional systematic biases were demonstrated with both reactance at 5 Hz and reactance area (AX) between the devices with a negative Bland-Altman regression slope. The printed airway resistance and standardised volume reactance confirmed the observations seen in patients. We have demonstrated that the impulse oscillation system and TremoFlo FOT demonstrate comparative bias, particularly when comparing airway reactance in patients. Our results highlight the need for further standardisation across FOT measurement devices, specifically using variable test loads for reactance standardisation.

Noise and biases in genomic data may underlie radically different hypotheses for the position of Iguania within Squamata.

Squamate reptiles are a major component of vertebrate biodiversity whose crown-clade traces its origin to a narrow window of time in the Mesozoic during which the main subclades diverged in rapid succession. Deciphering phylogenetic relationships among these lineages has proven challenging given the conflicting signals provided by genomic and phenomic data. Most notably, the placement of Iguania has routinely differed between data sources, with morphological evidence supporting a sister relationship to the remaining squamates (Scleroglossa hypothesis) and molecular data favoring a highly nested position alongside snakes and anguimorphs (Toxicofera hypothesis). We provide novel insights by generating an expanded morphological dataset and exploring the presence of phylogenetic signal, noise, and biases in molecular data. Our analyses confirm the presence of strong conflicting signals for the position of Iguania between morphological and molecular datasets. However, we also find that molecular data behave highly erratically when inferring the deepest branches of the squamate tree, a consequence of limited phylogenetic signal to resolve this ancient radiation with confidence. This, in turn, seems to result from a rate of evolution that is too high for historical signals to survive to the present. Finally, we detect significant systematic biases, with iguanians and snakes sharing faster rates of molecular evolution and a similarly biased nucleotide composition. A combination of scant phylogenetic signal, high levels of noise, and the presence of systematic biases could result in the misplacement of Iguania. We regard this explanation to be at least as plausible as the complex scenario of convergence and reversals required for morphological data to be misleading. We further evaluate and discuss the utility of morphological data to resolve ancient radiations, as well as its impact in combined-evidence phylogenomic analyses, with results relevant for the assessment of evidence and conflict across the Tree of Life.

Evaluating the applicability of using daily forecasts from seasonal prediction systems (SPSs) for agriculture: a case study of Nepal’s Terai with the NCEP CFSv2

Ensemble forecasts from dynamic seasonal prediction systems (SPSs) have the potential to improve decision-making for crop management to help cope with interannual weather variability. Because the reliability of crop yield predictions based on seasonal weather forecasts depends on the quality of the forecasts, it is essential to evaluate forecasts prior to agricultural applications. This study analyses the potential of Climate Forecast System version 2 (CFSv2) in predicting the Indian summer monsoon (ISM) for producing meteorological variables relevant to crop modeling. The focus area was Nepal’s Terai region, and the local hindcasts were compared with weather station and reanalysis data. The results showed that the CFSv2 model accurately predicts monthly anomalies of daily maximum and minimum air temperature (Tmax and Tmin) as well as incoming total surface solar radiation (Srad). However, the daily climatologies of the respective CFSv2 hindcasts exhibit significant systematic biases compared to weather station data. The CFSv2 is less capable of predicting monthly precipitation anomalies and simulating the respective intra-seasonal variability over the growing season. Nevertheless, the observed daily climatologies of precipitation fall within the ensemble spread of the respective daily climatologies of CFSv2 hindcasts. These limitations in the CFSv2 seasonal forecasts, primarily in precipitation, restrict the potential application for predicting the interannual variability of crop yield associated with weather variability. Despite these limitations, ensemble averaging of the simulated yield using all CFSv2 members after applying bias correction may lead to satisfactory yield predictions.

Reappraisal of the reliability of Doppler echocardiographic estimations for mean pulmonary artery pressure in patients with pulmonary hypertension: a study from a tertiary centre comparing four formulae.

Different Doppler echocardiography (DE) models have been proposed for estimation of mean pulmonary arterial pressures (PAMP) from tricuspid regurgitation (TR) jet velocity. We aimed to compare four TR-derived DE models in predicting the PAMP measured by right heart catheterization (RHC) in different groups of precapillary pulmonary hypertension (PH). A total of 287 patients with hemodynamically pre-capillary PH were enrolled (mean age = 51 ± 17.4 years, 59.9% female). All patients underwent DE before RHC (< 3 h) and four formulae (F) were used for TR-derived PAMP estimation (PAMP-DE). These were as follows: F1 = Chemla (0.61 × systolic pulmonary artery pressure [PASP] + 2); F2 = Friedberg (0.69 × PASP − 0.22), F3 = Aduen (0.70 × PASP); and F4 = Bech-Hanssen (0.65 × PASP − 1.2). The PASP and PAMP (mmHg) measured by RHC were 89.1 ± 30.4 and 55.8 ± 20.8, respectively. In the overall PH group, DE estimates for PASP (r = 0.59, P = 0.001) and PAMP (r = 0.56, P = 0.001 for all) showed significant correlations with corresponding RHC measures. Concordance was noted between Chemla and Bech-Hanssen, and Aduen and Bech-Hanssen. The Bland–Altman plot showed that Chemla and Bech-Hanssen overestimated and Friedberg and Aduen underestimated PAMP-RHC measures. Paired-t test showed significant systematic biases for Aduen and Bech-Hanssen while Passing-Bablok non-parametric analysis revealed significant systematic biases all four PAMP-DE estimates. There was poor agreement between PAMP-RHC measures and PAMP-DE deciles (Kappa values were 0.112, 0.097, 0.095, and 0.121, respectively). This study showed a poor agreement between PAMP-DE estimates by four TR-derived formulae and PAMP-RHC in patients with PH, regardless of the etiology. However, these results can not be fully extrapolated to a normal population and did not address the reliability of DE estimates for PH screening procedures.

Reliability and validity of a new accelerometer (Wimu®) system for measuring velocity during resistance exercises

This study had two main goals. The first was to determine the reliability of the Wimu® system (accelerometer) for mean velocity measurements during resistance exercises at 40% and 80% 1 repetition maximum (1RM). The second was to compare the results for the Wimu system to a linear encoder (gold standard) for mean velocity measurements when clipped to the bar during back squat exercises using the Smith machine. In all, 23 trained men (aged 22.3 ± 3.2 years) participated in this study. At maximum velocity in the concentric phase, they performed 10 repetitions with 40% 1RM and eight repetitions with 80% 1RM while using the Wimu system and T-Force linear encoder simultaneously to record data. Reliability was analysed using intraclass correlation, standard error of measurement and coefficient of variation. The validity was assessed using R2, intraclass correlation and Bland-Altman plots. The differences in test–retest reliability of both systems and systematic biases were non-significant ( p = 0.08–0.85) and very close to 0. The random errors averaged ±0.010 m/s. All the calculated coefficient of variations were less than 5% and all measurements had high intraclass correlations (mean: 0.936). Least-square linear regression and intraclass correlations for validity were very close to 1. Significant systematic biases were observed between the linear encoder and the Wimu system ( p &lt; 0.001), although the effect sizes were small (0.21–0.44) and standard error of the estimate in concentric and eccentric phases at both intensities was less than 0.030. In conclusion, the findings of this study suggest that the Wimu system is a reliable and valid tool for the assessment of mean velocity during the back squat exercise using the Smith machine. These findings could help coaches and sport researchers evaluate athletes performing resistance exercises similar to squats with a reliable, valid and portable tool.

Noninvasive Assessment of Oxygen Extraction Fraction in Chronic Ischemia Using Quantitative Susceptibility Mapping at 7 Tesla

The oxygen extraction fraction (OEF) is an effective metric to evaluate metabolic reserve in chronic ischemia. However, OEF is considered to be accurately measured only when using positron emission tomography (PET). Thus, we investigated whether OEF maps generated by magnetic resonance quantitative susceptibility mapping (QSM) at 7 Tesla enabled detection of OEF changes when compared with those obtained with PET. Forty-one patients with chronic stenosis/occlusion of the unilateral internal carotid artery or middle cerebral artery were examined using 7 Tesla-MRI and PET scanners. QSM images were obtained from 3-dimensional T2*-weighted images, using a multiple dipole-inversion algorithm. OEF maps were generated based on susceptibility differences between venous structures and brain tissues on QSM images. OEF ratios of the ipsilateral middle cerebral artery territory against the contralateral side were calculated on the QSM-OEF and PET-OEF images, using an anatomic template. The OEF ratio in the middle cerebral artery territory showed significant correlations between QSM-OEF and PET-OEF maps (r=0.69; P<0.001), especially in patients with a substantial increase in the PET-OEF ratio of 1.09 (r=0.79; P=0.004), although showing significant systematic biases for the agreements. An increased QSM-OEF ratio of >1.09, as determined by receiver operating characteristic analysis, showed a sensitivity and specificity of 0.82 and 0.86, respectively, for the substantial increase in the PET-OEF ratio. Absolute QSM-OEF values were significantly correlated with PET-OEF values in the patients with increased PET-OEF. OEF ratios on QSM-OEF images at 7 Tesla showed a good correlation with those on PET-OEF images in patients with unilateral steno-occlusive internal carotid artery/middle cerebral artery lesions, suggesting that noninvasive OEF measurement by MRI can be a substitute for PET.