Pooled error variance and covariance estimation of sparse in situ soil moisture sensor measurements in agricultural fields in Flanders

Accurately quantifying errors in soil moisture measurements from in situ sensors at fixed locations is essential for reliable state and parameter estimation in probabilistic soil hydrological modeling. This quantification becomes particularly challenging when the number of sensors per field or measurement zone (MZ) is limited. When direct calculation of errors from sensor data in a certain MZ is not feasible, we propose to pool systematic and random errors of soil moisture measurements for a specific measurement setup and derive a pooled error covariance matrix that applies to this setup across different fields and soil types. In this study, a pooled error covariance matrix was derived using soil moisture sensor measurements from three TEROS 10 (Meter Group, Inc., USA) sensors per MZ and soil moisture sampling campaigns conducted over three growing seasons, covering 93 cropping cycles in agricultural fields with diverse soil textures in Belgium. The MZ soil moisture estimated from a composite of nine soil samples with a small standard error (0.0038 m3 m−3) was considered the “true” MZ soil moisture. Based on these measurement data, we established a pooled linear recalibration of the TEROS 10 manufacturer's sensor calibration function. Then, for each individual sensor as well as for each MZ, we identified systematic offsets and temporally varying residual deviations between the calibrated sensor data and sampling data. Sensor deviations from the “true” MZ soil moisture were defined as observational errors and lump both measurement errors and representational errors. Since a systematic offset persists over time, it contributes to the temporal covariance of sensor observational errors. Therefore, we estimated the temporal covariance of observational errors of the individual and the MZ-averaged sensor measurements from the variance of the systematic offsets across all sensors and MZ averages, while the random error variance was derived from the variance of the pooled residual deviations. The total error variance was then obtained as the sum of these two components. Due to spatial soil moisture correlation, the variance and temporal covariance of MZ-averaged sensor observational errors could not be derived accurately from the individual sensor error variances and temporal covariances, assuming that the individual observational errors of the three sensors in a MZ were not correlated with each other. The pooled error covariance matrix of the MZ-averaged soil moisture measurements indicated a significant autocorrelation of sensor observational errors of 0.518, as the systematic error standard deviation (σα‾= 0.033 m3 m−3) was similar to the random error standard deviation (σϵ‾= 0.032 m3 m−3). To illustrate the impact of error covariance in probabilistic soil hydrological modeling, a case study was presented incorporating the pooled error covariance matrix in a Bayesian inverse modeling framework. These results demonstrate that the common assumption of uncorrelated random errors to determine parameter and model prediction uncertainty is not valid when measurements from sparse in situ soil moisture sensors are used to parameterize soil hydrological models. Further research is required to assess to what extent the error covariances found in this study can be transferred to other areas and how they impact parameter estimation in soil hydrological modeling.</p

Effects of Sleep Deprivation With 10 and 110 Minute Recovery Periods on the P300 in University Students

Auditory Evoked Potentials (AEPs) have been used as an objective measure to estimate hearing sensitivity and to study the integrity of the auditory neural pathways. Because the P300 is an endogenous AEP response, requiring participants to attend to an auditory stimulus to elicit a response, it has been used to assess the effects of sleep deprivation on cognitive processes such as attention and memory. There is evidence that the P300 response\u27s amplitude will decrease and that its latency will increase following 24 hours of sleep deprivation; confirming a slowing of cognitive processing following these adverse conditions. To date, there has been limited research about whether or not a brief recovery period will return the P300\u27s amplitude and latency to baseline values. The present study was designed to further study the effects of sleep deprivation and both 10 and 110 minute recovery periods on the P300 using a simple oddball paradigm (standard = 1000 Hz; target = 2000 Hz). AEPs were recorded for three conditions: baseline, after 23 to 26 hours of sleep deprivation, and following the recovery period. Participants consisted of 24 university students. Results revealed a significant increase in latency (p \u3c 0.05) and a significant decrease in amplitude (p \u3c 0.001 ) following sleep deprivation as well as a significant difference between the 10 minute and the 110 minute recovery groups (p \u3c 0.001). The results suggest sleep deprivation has an adverse effect on cognition and has provided preliminary research on the amount of rest needed to recover from these effects

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Human platelet lysate to substitute fetal bovine serum in hMSC expansion for translational applications: a systematic review

Foetal bovine serum (FBS), is the most commonly used culture medium additive for in vitro cultures, despite its undefined composition, its potential immunogenicity and possible prion/zoonotic transmission. For these reasons, significant efforts have been targeted at finding a substitute, such as serum free-media or human platelet-lysates (hPL). Our aim is to critically appraise the state-of-art for hPL in the published literature, comparing its impact with FBS. In June 2019 a systematic search of the entire Web of Science, Medline and PubMed database was performed with the following search terms: (mesenchymal stem cells) AND (fetal bovine serum OR fetal bovine calf) AND (human platelet lysate). Excluded from this search were review articles that were published before 2005, manuscripts in which mesenchymal stem cells (MSCs) were not from human sources, and when the FBS controls were missing. Based on our search algorithm, 56 papers were selected. A review of these papers indicated that hMSCs cultured with hPL showed a spindle-shaped elongated morphology, had higher proliferation indexes, similar cluster of differentiation (CD) markers and no significant variation in differentiation lineage (osteocyte, adipocyte, and chondrocyte) compared to those cultured with FBS. Main sources of primary hMSCs were either fat tissue or bone marrow; in a few studies cells isolated from alternative sources showed no relevant difference in their response. Despite the difference in medium choice and a lack of standardization of hPL manufacturing, the majority of publications support that hPL was at least as effective as FBS in promoting adhesion, survival and proliferation of hMSCs. We conclude that hPL should be considered a viable alternative to FBS in hMSCs culture-especially with a view for their clinical use