Corresponding Coefficient Of Variation Research Articles

An improved adaptive Kriging model for importance sampling reliability and reliability global sensitivity analysis

An improved adaptive Kriging model for importance sampling (IS) reliability and reliability global sensitivity analysis is proposed by introducing the IS density function into learning function. Considering the variance information of Kriging prediction, the formula of traditional IS method is extended to the form considering the uncertainty of symbol function. The estimated variance of failure probability caused by the prediction uncertainty of Kriging model is obtained, and the corresponding coefficient of variation (COV) is defined. Based on the standard deviation information of failure probability, a novel learning function considering the characteristic of IS density function is proposed, which are used to minimize the prediction uncertainty of Kriging. The corresponding stopping criterion is defined based on the COV information. In order to increase the likelihood that the selected sample points fall around the limit state boundary, the penalty function method is introduced to improve the learning function. Once the failure probability is obtained, the variable global sensitivity index is calculated through the failed sample set and Bayes theorem. The results show that: By introducing IS density function and penalty function into learning function, the sample points which contribute more to the failure probability can be obtained more effectively in IS method. The proposed method has high accuracy and efficiency compared with traditional Kriging-based IS method.

New chemiluminescent enzyme immunoassay for quantitative measurement of Mac-2 binding protein glycosylation isomer in chronic liver disease.

This study aimed to evaluate the quantitative measurement of Mac-2 binding protein glycosylation isomer (M2BPGi) levels using the new chemiluminescent enzyme immunoassay. The data of a total of 347 patients with hepatitis C virus (HCV) infection and 150 health volunteers from 13 locations in Japan were evaluated. The quantitative system for measuring M2BPGi-Qt levels was based on a new chemiluminescent enzyme immunoassay. We evaluated the reproducibility and quantitation range in quantitative M2BPGi-Qt measurement. We also investigated the confidence ratio of M2BPGi-Qt levels measured by the new quantitative system to M2BPGi levels measured by the current semi-quantitative system for validating the clinical utility of the new method. The reproducibility of M2BPGi-Qt in HCV samples with negative, positive 1+, and positive 2+ was 0.77 ± 0.02AU/mL, 2.25 ± 0.03AU/mL, and 6.55 ± 0.21AU/mL, respectively, and the corresponding coefficient of variation (CV)s were 2.1%, 1.3%, and 3.2%, respectively. The range of quantification assessment resulted that all CVs showed less than 5% in investigated range. Sample stability testing found that the mean percentage difference between the pre- and post-storage values of 6 samples ranged between 96.2 and 103.9%. The correlation coefficient between M2BPGi and M2BPGi-Qt in patients with HCV and the healthy volunteers was 0.986 and 0.991, respectively. M2BPGi-Qt could be quantitatively assessed in a patient with over 20 C.O.I. Compared with qualitative methods, the M2BPGi quantitative measurement system could provide a numerical value unaffected by interpretation bias, and measurements are more precise at high M2BPGi levels.

Moment curvature response of composite UHPC filled hollow structural steel cross-sections

A mechanics based analytical method for obtaining the complete moment–curvature response of composite hollow structural steel (HSS) and ultra high performance concrete (UHPC) cross-sections is presented. Flexural response at the cross-sectional level is traced past the local buckling of the steel elements and up to the exhaustion of UHPC and steel material capacity. The proposed method is validated using experimental data from seven flexural tests on composite HSS-UHPC beams. Flexural failure mode is classified as either a UHPC compression-controlled failure, UHPC fiber tension-controlled failure, or a balanced failure. Behavioral differences between the cross-sections that fall into these three categories are discussed in terms of flexural capacity, curvature ductility, and relative contributions of HSS and UHPC to flexural capacity. Flexural response of the composite HSS-UHPC cross-section is compared to that of the bare HSS cross-section. The enhancement in flexural capacity and curvature ductility, for UHPC fiber tension-controlled sections compared to the bare HSS cross-section, was 52% and 79%, respectively. For composite cross-sections that feature a balanced failure, the increase in flexural capacity and curvature ductility, compared to the bare HSS cross-section, was 37% and 35%, respectively. Closed form formulations are proposed to identify the flexural failure mode and predict flexural capacity. The influence of various parameters, such as HSS material grade, size of cross-section, and UHPC material characteristics on the complete flexural response of the cross-section is investigated. The average ratio and corresponding coefficient of variation (COV) of tested to computed flexural strength obtained using the proposed procedure was 1.06 and 21.28%, respectively. Similarly, the average ratio and COV of tested to calculated flexural strength obtained using the proposed closed form formulations was 1.07 and 22.18%, respectively.

Development and validation of HPLC-MS/MS method for simultaneous analysis of B vitamins present naturally or after fortification in fruit juices

In this study, a multivitamin analysis method with a run time of 20 min was developed for nine major B vitamins in fruit juices using HPLC coupled with a triple quadrupole mass spectrometer. A reverse phase column with ammonium formate buffers in methanol and water as mobile phases under gradient elution mode were used to accomplish chromatographic separation. A simple dilute and shoot method was used for sample preparation. A calibration and accuracy study for method validation was conducted. The accuracy profiles were created using measurement uncertainty estimated from the validation data according to the ISO/DTS 21748. The proportional bias due to the matrix effect were ranging between 80% and 115% in the matrices investigated in this study. The measurement uncertainty and the corresponding coefficient of variation were within the acceptable limits defined in the literature and international regulatory standards i.e. EU regulation. The limits of quantitation were low enough to prove fitness for purpose for all vitamins except cyanocobalamin. The study concludes with a method with the potential to be used in quality control laboratories for high throughput routine vitamin analysis.

Motion compensated renal diffusion weighted imaging.

To assess the effect of respiratory motion and cardiac driven pulsation in renal DWI and to examine asymmetrical velocity-compensated diffusion encoding waveforms for robust ADC mapping in the kidneys. The standard monopolar Stejskal-Tanner pulsed gradient spin echo (pgse) and the asymmetric bipolar velocity-compensated (asym-vc) diffusion encoding waveforms were used for coronal renal DWI at 3T. The robustness of the ADC quantification in the kidneys was tested with the aforementioned waveforms in respiratory-triggered and breath-held cardiac-triggered scans at different trigger delays in 10 healthy subjects. The pgse waveform showed higher ADC values in the right kidney at short trigger delays in comparison to longer trigger delays in the respiratory triggered scans when the diffusion gradient was applied in the feet-head (FH) direction. The coefficient of variation over all respiratory trigger delays, averaged over all subjects was 0.15 for the pgse waveform in the right kidney when diffusion was measured in the FH direction; the corresponding coefficient of variation for the asym-vc waveform was 0.06. The effect of cardiac driven pulsation was found to be small in comparison to the effect of respiratory motion. Short trigger delays in respiratory-triggered scans can cause higher ADC values in comparison to longer trigger delays in renal DWI, especially in the right kidney when diffusion is measured in the FH direction. The asym-vc waveform can reduce ADC variation due to respiratory motion in respiratory-triggered scans at the cost of reduced SNR compared to the pgse waveform.

VARIABILITY IN CENTRAL AND LOCAL MEASUREMENT OF FVC IN IDIOPATHIC PULMONARY FIBROSIS: AN EXPLORATORY ANALYSIS FROM THE CAPACITY, ASCEND, AND RIFF (COHORT A) TRIALS

VARIABILITY IN CENTRAL AND LOCAL MEASUREMENT OF FVC IN IDIOPATHIC PULMONARY FIBROSIS: AN EXPLORATORY ANALYSIS FROM THE CAPACITY, ASCEND, AND RIFF (COHORT A) TRIALS

Hybrid Krill Herd-ANN Model for Prediction Strength and Stiffness of Bolted Connections

The behavior of beam-to-column connections significantly influences the stability, strength, and stiffness of steel structures. This is particularly important in extreme non-elastic responses, i.e., earthquakes, and sudden column removal, as the fluctuation in strength and stiffness affects both supply and demand. Accordingly, it is essential to accurately estimate the strength and stiffness of connections in the analysis of and design procedures for steel structures. Beginning with the state-of-the-art, the capacity of three available component-based mechanical models to estimate the complex mechanical properties of top- and seat-angle connections with double-web angles (TSACWs), with variable parameters, were investigated. Subsequently, a novel hybrid krill herd algorithm-artificial neural network (KHA-ANN) model was proposed to acquire an informational model from the available experimental dataset. Using several statistical metrics, including the corresponding coefficient of variation (CoV), correlation coefficient (R), and the correlation coefficient provided by the Taylor diagram, this study revealed that the krill herd-ANN model achieved the most reliable predictive accuracy for the strength and stiffness of top- and seat-angle connections with double web angles.

Shear model mSM-c for slender reinforced concrete members without shear reinforcement subjected to fatigue loads

Research on shear behaviour and shear capacity of reinforced concrete members without shear reinforcement is always of particular interest, especially the development of a general model for design of shear capacity of various reinforced concrete members under different load actions. One of the recent solutions to this problem is the mechanical shear model mSM, previously developed by the author, which was derived exclusively based on mechanical principles and mathematical formulations. In this paper, an extend formulation of this model, named mSM-c, for members under cyclic loads is presented. In contrast to existing methods, the new approach considers the fatigue degradation of shear capacity on the material level, taking into account the mechanical properties of concrete in detail, including the tensile strength, the fracture energy and the bond between concrete and reinforcement. The model is extensively verified using the results of shear tests published by other authors. An evaluation of the experimental-to-calculated ratio Vexp/Vcal for a shear test database of 108 simply supported beams under concentrated loads using mSM-c yielded a mean value of 1.02 and a corresponding coefficient of variation of 11%, showing a notable improvement in prediction accuracy when compared to some existing shear models. In addition, an analysis of the fatigue shear capacity of concrete members included in the shear test database shows that fatigue creep of the bond between concrete and reinforcement reduces the shear capacity by about 3%.

Time-Course Changes in Optic Nerve Head Blood Flow and Retinal Nerve Fiber Layer Thickness in Eyes with Open-angle Glaucoma

To determine whether decreased optic nerve head (ONH) blood flow (BF) precedes or follows decreased circumpapillary retinal nerve fiber layer thickness (cpRNFLT) in eyes with open-angle glaucoma (OAG). Retrospective, longitudinal study. This study followed up 350 eyes of 225 OAG patients for at least 2 years and collected data from each patient from at least 5 examinations obtained with laser speckle flowgraphy (LSFG) and OCT. In the superior, temporal, and inferior ONH quadrants, tissue area mean blur rate (MT), representing ONH tissue BF, was measured with LSFG, whereas cpRNFLT was measured with OCT. A multivariate linear mixed-effects model was used to identify potential predictors of faster MT decrease, adjusting for possible confounding factors. Based on these results, each quadrant of each patient was assigned a risk point if the quadrant was the superior or temporal, if patient age was older than the median (61 years), and if patient pulse rate was higher than median (74 beats per minute). The quadrants were then compared with a mixed-effects Cox model for MT and cpRNFLT changes, defined as a difference between the baseline value and the values from the latest 2 consecutive follow-up visits of more than 1.96× the corresponding coefficient of variation. Ophthalmic and systemic variables and MT and cpRNFLT in the superior, temporal, and inferior quadrants. The multivariate model showed that MT decrease was faster in older patients with higher pulse rate and slower in inferior quadrants (P < 0.05). Quadrants with 0 risk points showed primary cpRNFLT decrease (P= 0.048), 1-risk point quadrants showed simultaneous cpRNFLT and MT decrease (P= 0.260), and 2-risk point and 3-risk point quadrants showed primary MT decrease (P < 0.001). Older patients with higher pulse rate are at greater risk of a primary reduction in ONH tissue BF, that is, preceding cpRNFLT decrease, in the superior and temporal quadrants.

Free-breathing whole-heart multi-slice myocardial T1 mapping in 2 minutes.

To develop and validate a saturation-delay-inversion recovery preparation, slice tracking and multi-slice based sequence for measuring whole-heart native T1 . The proposed free-breathing sequence performs T1 mapping of multiple left-ventricular slices by slice-interleaved acquisition to collect 10 electrocardiogram-triggered single-shot slice-selective images for each slice. A saturation-delay-inversion recovery pulse is used for T1 preparation. Prospective slice tracking by the diaphragm navigator and retrospective registration are used to reduce through-plane and in-plane motion, respectively. The proposed sequence was validated in both phantom and human subjects (12 healthy subjects and 15 patients who were referred for a clinical cardiac MR exam) and compared with saturation recovery single-shot acquisition (SASHA) and modified Look-Locker inversion recovery (MOLLI). Phantom T1 measured by the proposed sequence had excellent agreement (R2 =0.99) with the ground-truth T1 and was insensitive to heart rate. In both healthy subjects and patients, the proposed sequence yielded nine left-ventricular T1 maps per volume in less than 2 minutes (healthy volunteers: 1.8±0.4minutes; patients: 1.9±0.2minutes). The average T1 of whole left ventricle for all healthy subjects and patients were 1560±61 and 1535±49ms by SASHA, 1208±42 and 1233±56ms by MOLLI5(3)3, and 1397±34 and 1433±56ms by the proposed sequence, respectively. The corresponding coefficient of variation of T1 were 6.2±1.4% and 5.8±1.6%, 5.3±1.1% and 5.1±0.8%, and 4.9±0.8% and 4.5±0.8%, respectively. The proposed sequence enables quantification of whole heart T1 with good accuracy and precision in less than 2 minutes during free breathing.

Prediction of the load and deflection response of concrete deep beams reinforced with FRP bars

The load and deflection response of six concrete deep beams longitudinally reinforced with glass fiber-reinforced polymer (GFRP) bars having shear span to depth ratio of 0.5 to 1.0 were presented in this paper. The existing model originally proposed for the prediction of shear strength and the deflection at the ultimate stage of concrete deep beams longitudinally reinforced with steel reinforcement, using the Softened Strut- and-Tie (SST) concept is modified to account for the influence of FRP longitudinal bars in the deep beam. The magnitude of strut efficiency factor was proposed based on the regression analysis of 47 test data. The model is useful for the prediction of load and deflection response of FRP reinforced concrete deep beams up to ultimate stage. The degradation of the stiffness due to the progressive cracking of the concrete is accounted for in this model. The predicted load-deflection response of the six test beams in this study was found to be comparable to the corresponding experimental data. The load and the mid-span deflection at ultimate stage of 53 simply supported deep beams longitudinally reinforced with FRP bars were also predicted using the proposed model. The mean of the ratio of the experimental load to the predicted load and deflection at ultimate stage for the 53 beams is found to be 1.05 and 1.03 respectively with the corresponding coefficient of variation (CoV) of 29.5% and 40.8% respectively.

Variability and trends in runoff in the rivers of British Columbia's Coast and Insular Mountains

AbstractThis study examines the 1914–2015 runoff trends and variability for 136 rivers draining British Columbia's Coast and Insular Mountains. Rivers are partitioned into eastward and westward flowing rivers based on flow direction from the Coast Mountains. Thus, eastward and westward runoff trends and influence of topography on runoff are explored. Our findings indicate that rivers flowing eastward to the Nechako and Chilcotin plateaus contribute the lowest annual runoff compared to westward rivers where runoff is high. Low interannual runoff variability is evident in westward rivers and their alpine watersheds, whereas eastward rivers exhibit high interannual runoff variability. On Vancouver Island, some of the rivers with the highest annual runoff exhibit high interannual variability. A significant (p &lt; .05) negative correlation exists between mean annual runoff (Rm) and latitude, gauged area, mean elevation, and its corresponding coefficient of variation. However, a significant positive correlation was found between the glacierized area of mountainous regions and Rm. The mean coefficient of variation in annual runoff is significantly negatively correlated with latitude and glacierized area, but significantly positively correlated with longitude. Annual and seasonal runoff trend analyses of each river were performed for an early (1936–2015), a middle (1966–2015), and a late (1986–2015) period using the Mann–Kendall test. Trend analyses revealed a shift towards more positive detectable (signal‐to‐noise ratio &gt; 1) trends in annual and seasonal runoff from the middle to the late period across the study domain. Most positive detectable seasonal runoff trends in the middle period occur in spring in glacierized westward rivers located &gt;1,200 m, whereas in the late period, they all occur in fall and are regionally coherent around Vancouver Island and south coastal BC. Rivers draining eastward exhibit more positive trends over 1986–2015 compared to westward rivers. This study provides crucial information on the hydrology of mountain watersheds across British Columbia's coast in response to Pacific Decadal Oscillation phase changes, the elevational amplification of regional climate change, and their influences on precipitation and glacier retreat.

An Inter-Laboratory Comparison for the Urinary Acrolein Biomarker 3-Hydroxypropyl-Mercapturic Acid (3-HPMA)

Summary An inter-laboratory comparison study on the acrolein biomarker of exposure 3-hydroxypropyl-mercapturic acid (3-HPMA) with 12 laboratories from 7 globally distributed countries was performed. The laboratories received coded triplicates of 4 spiked and lyophilized urine samples (LU, 12 samples) as well as 5 authentic urine pool samples (PU, 15 samples) covering the 3-HPMA concentration range from background (non-smoking) to heavy smoking levels for analysis by using their own (in-house) analytical method. All laboratories applied liquid chromatography with tandem mass spectrometry (LC-MS/MS), with most of them (10 of 12) using solid phase extraction (SPE) as sample work-up procedure. The intra-laboratory variation (indicating repeatability) was determined by calculating the standard deviation (sr) and the coefficient of variation (CVr) of the triplicates, whereas the inter-laboratory variation (indicating reproducibility) was determined by calculating the standard deviation between laboratories (sR) and the corresponding coefficient of variation (CVR). After removal of outlier samples or laboratories, the mean CVr values for LU and PU test samples ranged from 2.1–3.6% (mean: 2.8%) and 2.4–3.7% (mean: 3.3%), respectively, indicating good repeatability for the determination of 3-HPMA in both sample types. CVR for LU and PU test samples ranged from 9.1–31.9% (mean: 18.8%) and 13.9–27.0% (mean: 18.5%), respectively, indicating limited reproducibility in 3-HPMA analysis for both sample types. Re-calculation of the PU results by applying an embedded calibration (EC), derived from the reported peak areas for the LU test samples, somewhat improved the CVR values (range: 9.6–28.8%, mean: 16.7%). It is concluded that the intra-laboratory variation (repeatability) in the determination of 3-HPMA in urine is in general acceptable in the participating laboratories, while the inter-laboratory variability requires further improvement. The relatively small reduction in the inter-laboratory variability (sR and CVR) by applying an EC suggests that other methodological factors than the standard reference material for 3-HPMA have to be addressed to achieve further improvement in reproducibility.

Editors’ Note

Summary An inter-laboratory comparison study on the acrolein biomarker of exposure 3-hydroxypropyl-mercapturic acid (3-HPMA) with 12 laboratories from 7 globally distributed countries was performed. The laboratories received coded triplicates of 4 spiked and lyophilized urine samples (LU, 12 samples) as well as 5 authentic urine pool samples (PU, 15 samples) covering the 3-HPMA concentration range from background (non-smoking) to heavy smoking levels for analysis by using their own (in-house) analytical method. All laboratories applied liquid chromatography with tandem mass spectrometry (LC-MS/MS), with most of them (10 of 12) using solid phase extraction (SPE) as sample work-up procedure. The intra-laboratory variation (indicating repeatability) was determined by calculating the standard deviation (sr) and the coefficient of variation (CVr) of the triplicates, whereas the inter-laboratory variation (indicating reproducibility) was determined by calculating the standard deviation between laboratories (sR) and the corresponding coefficient of variation (CVR). After removal of outlier samples or laboratories, the mean CVr values for LU and PU test samples ranged from 2.1–3.6% (mean: 2.8%) and 2.4–3.7% (mean: 3.3%), respectively, indicating good repeatability for the determination of 3-HPMA in both sample types. CVR for LU and PU test samples ranged from 9.1–31.9% (mean: 18.8%) and 13.9–27.0% (mean: 18.5%), respectively, indicating limited reproducibility in 3-HPMA analysis for both sample types. Re-calculation of the PU results by applying an embedded calibration (EC), derived from the reported peak areas for the LU test samples, somewhat improved the CVR values (range: 9.6–28.8%, mean: 16.7%). It is concluded that the intra-laboratory variation (repeatability) in the determination of 3-HPMA in urine is in general acceptable in the participating laboratories, while the inter-laboratory variability requires further improvement. The relatively small reduction in the inter-laboratory variability (sR and CVR) by applying an EC suggests that other methodological factors than the standard reference material for 3-HPMA have to be addressed to achieve further improvement in reproducibility.

Altered Neuronal Firing Pattern of the Basal Ganglia Nucleus Plays a Role in Levodopa-Induced Dyskinesia in Patients with Parkinson’s Disease

Background: Levodopa therapy alleviates the symptoms of Parkinson’s disease (PD), but long-term treatment often leads to motor complications such as levodopa-induced dyskinesia (LID).Aim: To explore the neuronal activity in the basal ganglia nuclei in patients with PD and LID.Methods: Thirty patients with idiopathic PD (age, 55.1 ± 11.0 years; disease duration, 8.7 ± 5.6 years) were enrolled between August 2006 and August 2013 at the Xuanwu Hospital, Capital Medical University, China. Their Hoehn and Yahr (1967) scores ranged from 2–4 and their UPDRS III scores were 28.5 ± 5.2. Fifteen of them had severe LID (UPDRS IV scores of 6.7 ± 1.6). Microelectrode recording was performed in the globus pallidus internus (GPi) and subthalamic nucleus (STN) during pallidotomy (n = 12) or STN deep brain stimulation (DBS; bilateral, n = 12; unilateral, n = 6). The firing patterns and frequencies of various cell types were analyzed by assessing single cell interspike intervals (ISIs) and the corresponding coefficient of variation (CV).Results: A total of 295 neurons were identified from the GPi (n = 12) and STN (n = 18). These included 26 (8.8%) highly grouped discharge, 30 (10.2%) low frequency firing, 78 (26.4%) rapid tonic discharge, 103 (34.9%) irregular activity, and 58 (19.7%) tremor-related activity. There were significant differences between the two groups (p < 0.05) for neurons with irregular firing, highly irregular cluster-like firing, and low-frequency firing.Conclusion: Altered neuronal activity was observed in the basal ganglia nucleus of GPi and STN, and may play important roles in the pathophysiology of PD and LID.

Symmetric -charts: Sensitivity to nonnormality and control-limit estimation

ABSTRACTWe study the classical symmetric -chart with control limits set k standard deviations from the known in-control mean. The standard deviation is estimated with in-control data, in what we refer to as Phase-I. We consider three performance measures: the average run length (ARL), the standard deviation of the conditional average run length (SDARL), and the corresponding coefficient of variation. Modeling the data as independent and identically distributed, with marginal distributions chosen from the Johnson family, we investigate in-control and out-of-control sensitivities to three factors: the third and fourth standardized moments of the data distribution and the number of Phase-I observations. Considering both bounded and unbounded data distributions, our analytical, numerical, and Monte Carlo simulation results show that nonnormality has a substantial effect on all three performance measures; and the effects are nonmonotonic in both skewness and kurtosis. We show that all three performance measures are flawed when estimating the standard deviation. In particular, we show that ARL and SDARL values increase, eventually becoming infinite, as the number of Phase-I observations decreases, even in cases where run length is finite with probability one. We show analytically that, for bounded data distributions with any finite shift, estimating the standard deviation sometimes results in infinite ARL and SDARL values.

Constant-Damage Yield Strength Spectra for RC Structures Using Modified Park-Ang Damage Model

In this study, constant-damage yield strength spectrum (CDYSS), which is defined as the yield strength demand of a single-degree-of-freedom (SDOF) system of varying natural vibration period with the target constant damage index and specified ductility capacity, is derived by averaging the nonlinear time-history analysis results of a SDOF system under different earthquake ground motions. A modified Park-Ang damage model proposed by the authors, eliminating its non-convergence problem both at upper and lower limits with higher precision and smaller scatter, is adopted to calculate the damage index of the SDOF system. In the construction of CDYSS, 641 sets of earthquake ground motion records are adopted and classified into 12 groups in line with Chinese code for seismic design of buildings. The yield strength demands of SDOF systems with given ductility capacity are obtained through trial and error method. Then, the mean CDYSS and the corresponding coefficient of variation for different group of site soil conditions are calculated. The effects of ductility capacity and local site soil conditions on CDYSS are discussed. Lastly, the empirical formulas of CDYSS are developed by multivariable nonlinear regression analysis and compared with actual CDYSS.

Lameness detection via leg-mounted accelerometers on dairy cows on four commercial farms

Lameness in dairy herds is traditionally detected by visual inspection, which is time-consuming and subjective. Compared with healthy cows, lame cows often spend longer time lying down, walk less and change behaviour around feeding time. Accelerometers measuring cow leg activity may assist farmers in detecting lame cows. On four commercial farms, accelerometer data were derived from hind leg-mounted accelerometers on 348 Holstein cows, 53 of them during two lactations. The cows were milked twice daily and had no access to pasture. During a lactation, locomotion score (LS) was assessed on average 2.4 times (s.d. 1.3). Based on daily lying duration, standing duration, walking duration, total number of steps, step frequency, motion index (MI, i.e. total acceleration) for lying, standing and walking, eight accelerometer means and their corresponding coefficient of variation (CV) were calculated for each week immediately before an LS. A principal component analysis was performed to evaluate the relationship between the variables. The effects of LS and farm on the principal components (PC) and on the variables were analysed in a mixed model. The first four PC accounted for 27%, 18%, 12% and 10% of the total variation, respectively. PC1 corresponded to Activity variability due to heavy loading by five CV variables related to standing and walking. PC2 corresponded to Activity level due to heavy loading by MI walking, MI standing and walking duration. PC3 corresponded to Recumbency due to heavy loading by four variables related to lying. PC4 corresponded mainly to Stepping due to heavy loading by step frequency. Activity variability at LS4 was significantly higher than at the lower LS levels. Activity level was significantly higher at LS1 than at LS2, which was significantly higher than at LS4. Recumbency was unaffected by LS. Stepping at LS1 and LS2 was significantly higher than at LS3 and LS4. Activity level was significantly lower on farm 3 compared with farms 1 and 2. Stepping was significantly lower on farms 1 and 3 compared with farms 2 and 4. MI standing indicated increased restlessness while standing when cows increased from LS3 to LS4. Lying duration was only increased in lame cows. In conclusion, Activity level differed already between LS1 and LS2, thus detecting early signs of lameness, particularly through contributions from walking duration and MI walking. Lameness detection models including walking duration, MI walking and MI standing seem worthy of further investigation.

Divergent apparent temperature sensitivity of terrestrial ecosystem respiration

Aims Recent studies revealed convergent temperature sensitivity of ecosystem respiration (Re) within aquatic ecosystems and between terrestrial and aquatic ecosystems. We do not know yet whether various terrestrial ecosystems have consistent or divergent temperature sensitivity. Here, we synthesized 163 eddy covariance flux sites across the world and examined the global variation of the apparent activation energy (Ea), which characterizes the apparent temperature sensitivity of and its interannual variability (IAV) as well as their controlling factors. Methods We used carbon fluxes and meteorological data across FLUXNET sites to calculate mean annual temperature, temperature range, precipitation, global radiation, potential radiation, gross primary productivity and Re by averaging the daily values over the years in each site. Furthermore, we analyzed the sites with >8 years data to examine the IAV of Ea and calculated the standard deviation of Ea across years at each site to characterize IAV. Important Findings The results showed a widely global variation of Ea, with significantly lower values in the tropical and subtropical areas than in temperate and boreal areas, and significantly higher values in grasslands and wetlands than that in deciduous broadleaf forests and evergreen forests. Globally, spatial variations of Ea were explained by changes in temperature and an index of water availability with differing contribution of each explaining variable among climate zones and biomes. IAV and the corresponding coefficient of variation of Ea decreased with increasing latitude, but increased with radiation and corresponding mean annual temperature. The revealed patterns in the spatial and temporal variations of Ea and its controlling factors indicate divergent temperature sensitivity of R-e, which could help to improve our predictive understanding of R-e in response to climate change.

Creep behavior of basalt fiber reinforced polymer tendons for prestressing application

This paper investigates the creep behavior of newly developed basalt fiber reinforced polymer (BFRP) tendons for prestressing application. The creep strain to time relationship, creep rate and residual strength were experimentally studied and the relevant mechanism was elaborated. Furthermore, the creep rupture stress was predicted based on statistical analysis. The results show that the creep strain to time relationship of BFRP tendons depends highly on the stress level applied. The creep rate of BFRP tendons under low levels of stress remains in low and steady values. Meanwhile, the residual strength of BFRP after 1000h of sustained load still reaches approximately 95% of its initial tensile strength and the corresponding coefficient of variation (CV) is much less than the original CV. For prestressing application, the creep rupture stress limit for BFRP tendons can be adopted up to 52% of its tensile strength according to the reliability based analysis.