Hydrogeological effects on terrestrial gravity measurements

For the 20 last years, terrestrial and satellite gravity measurements have reached such a precision that they allow for identification of the signatures from water storage fluctuations. In particular, hydrogeological effects induce significant time-correlated signature in the gravity time series. Gravity response to rainfall is a complex function of the local geologic and climatic conditions, e.g., rock porosity, vegetation, evaporation, and runoff rates. The gravity signal combines contributions from many geophysical processes, source separation being a major challenge. At the local scale and short-term, the associated gravimetric signatures often exceed the tectonic and GIA effects, and monitoring gravity changes is a source of information on local groundwater mass balance, and contributes to model calibrations. Some aquifer main characteristics can then be inferred by combining continuous gravity, geophysical and hydrogeological measurements. In Membach, Belgium, a superconducting gravimeter has monitored gravity continuously for more than 24 years. This long time series, together with 300 repeated absolute gravity measurements and environmental monitoring, has provided valuable information on the instrumental, metrological, hydrogeological and geophysical points of view. This has allowed separating the signal sources and monitoring partial saturation dynamics in the unsaturated zone, convective precipitation and evapotranspiration at a scale of up to 1 km², for signals smaller than 1 nm/s², equivalent to 2.5 mm of water. Based on this experience, another superconducting gravimeter was installed in 2014 in the karst zone of Rochefort, Belgium. In a karst area, where the vadose zone is usually thicker than in other contexts, combining gravity measurements at the surface and inside accessible caves is a way to separate the contribution from the unsaturated zone lying between the two instruments, from the saturated zone underneath the cave, and the common mode effects from the atmosphere or other regional processes. Those experiments contribute to the assessment of the terrestrial hydrological cycle, which is a major challenge of the geosciences associated with key societal issues: availability of freshwater, mitigation of flood hazards, or measurement of evapotranspiration

Hydrogeological effects on terrestrial gravity measurements

For the 20 last years, terrestrial and satellite gravity measurements have reached such a precision that they allow for identification of the signatures from water storage fluctuations. In particular, hydrogeological effects induce significant time-correlated signature in the gravity time series. Gravity response to rainfall is a complex function of the local geologic and climatic conditions, e.g., rock porosity, vegetation, evaporation, and runoff rates. The gravity signal combines contributions from many geophysical processes, source separation being a major challenge. At the local scale and short-term, the associated gravimetric signatures often exceed the tectonic and GIA effects, and monitoring gravity changes is a source of information on local groundwater mass balance, and contributes to model calibrations. Some aquifer main characteristics can then be inferred by combining continuous gravity, geophysical and hydrogeological measurements. In Membach, Belgium, a superconducting gravimeter has monitored gravity continuously for more than 24 years. This long time series, together with 300 repeated absolute gravity measurements and environmental monitoring, has provided valuable information on the instrumental, metrological, hydrogeological and geophysical points of view. This has allowed separating the signal sources and monitoring partial saturation dynamics in the unsaturated zone, convective precipitation and evapotranspiration at a scale of up to 1 km², for signals smaller than 1 nm/s², equivalent to 2.5 mm of water. Based on this experience, another superconducting gravimeter was installed in 2014 in the karst zone of Rochefort, Belgium. In a karst area, where the vadose zone is usually thicker than in other contexts, combining gravity measurements at the surface and inside accessible caves is a way to separate the contribution from the unsaturated zone lying between the two instruments, from the saturated zone underneath the cave, and the common mode effects from the atmosphere or other regional processes. Those experiments contribute to the assessment of the terrestrial hydrological cycle, which is a major challenge of the geosciences associated with key societal issues: availability of freshwater, mitigation of flood hazards, or measurement of evapotranspiration

Treatment failure and hospital readmissions in severe COPD exacerbations treated with azithromycin versus placebo - A post-hoc analysis of the BACE randomized controlled trial

Background: In the BACE trial, a 3-month (3 m) intervention with azithromycin, initiated at the onset of an infectious COPD exacerbation requiring hospitalization, decreased the rate of a first treatment failure (TF); the composite of treatment intensification (TI), step-up in hospital care (SH) and mortality. Objectives: (1) To investigate the intervention's effect on recurrent events, and (2) to identify clinical subgroups most likely to benefit, determined from the incidence rate of TF and hospital readmissions. Methods: Enrolment criteria included the diagnosis of COPD, a smoking history of ≥10 pack-years and ≥ 1 exacerbation in the previous year. Rate ratio (RR) calculations, subgroup analyses and modelling of continuous variables using splines were based on a Poisson regression model, adjusted for exposure time. Results: Azithromycin significantly reduced TF by 24% within 3 m (RR = 0.76, 95%CI:0.59;0.97, p = 0.031) through a 50% reduction in SH (RR = 0.50, 95%CI:0.30;0.81, p = 0.006), which comprised of a 53% reduction in hospital readmissions (RR = 0.47, 95%CI:0.27;0.80; p = 0.007). A significant interaction between the intervention, CRP and blood eosinophil count at hospital admission was found, with azithromycin significantly reducing hospital readmissions in patients with high CRP (> 50 mg/L, RR = 0.18, 95%CI:0.05;0.60, p = 0.005), or low blood eosinophil count (<300cells/μL, RR = 0.33, 95%CI:0.17;0.64, p = 0.001). No differences were observed in treatment response by age, FEV1, CRP or blood eosinophil count in continuous analyses. Conclusions: This post-hoc analysis of the BACE trial shows that azithromycin initiated at the onset of an infectious COPD exacerbation requiring hospitalization reduces the incidence rate of TF within 3 m by preventing hospital readmissions. In patients with high CRP or low blood eosinophil count at admission this treatment effect was more pronounced, suggesting a potential role for these biomarkers in guiding azithromycin therapy. Trial registration: ClinicalTrials.gov number. NCT02135354. © 2019 The Author(s)

Extreme hydrometeorological events, a challenge for geodesy and seismology networks

The use of seismometer and gravimeter captures complementary data and brings a new understanding of the July 2021 catastrophic floods in Belgium. A sudden increase in seismic noise coincides with the testimony reporting on a 'tsunami' downstream of the Membach geophysical station, along the Vesdre valley. Concurrently, the gravimeter evidenced a rising saturation of the weathered zone, thus showing less and less water accumulation. When rain re-intensified after a 3-hour break, the saturated state of the subsoil induced an accelerated increase of the runoff, as revealed by the Vesdre River flow, in a much stronger way than during the rainy episodes just before. We show that a gravimeter can detect in real-time the saturation of the catchment subsoil and soil. This saturation resulted, when the rain re-intensified, in a sudden, devastating, and deadly flood. This opens perspectives to use real-time gravity for early warnings of such events.13. Climate actio

Extreme Hydrometeorological Events, a Challenge for Gravimetric and Seismology Networks

Extreme events will become more common due to global change, requiring enhanced monitoring and pushing conventional observation networks to their limits. This encourages us to combine all the possible sources of information to obtain a complete picture of extreme events and their evolution. This commentary builds on an example of the July 2021 catastrophic floods that hit northwest Europe, for which the use of seismometer and gravimeter captures complementary data and brings a new understanding of the event and its dynamics. A sudden increase in seismic noise coincides with the testimony reporting on a “tsunami” downstream of the geophysical station. Concurrently, the gravimeter showed increasing saturation of the weathered zone, showing less and less water accumulation and increasing runoff. When rain re-intensified after a 3-hr break, the subsoil's saturation state induced an accelerated runoff increase, as revealed by the river flow, in a much stronger way than during the rainy episodes just before. We show that the gravimeter detected the saturation of the catchment subsoil and soil in real-time. When the rain re-intensified, this saturation resulted in a sudden, devastating, and deadly flood. Our study opens up the possibility of integrating real-time gravity in early warning systems for such events

Assessment centers: is it worthwhile to use a competencies-based framework?

Over the past several decades, assessment centers have enjoyed increased popularity as both development and selection tools. Indeed, this method which evaluates candidates on several job-related dimensions through various simulation exercises and by multiple trained assessors has been shown to have a substantial criterion-related validity, i.e. to be a valid predictor of performance in a wide range of jobs. In contrast, evidence for the construct-related validity of assessment centers dimensions has been more mixed. The recent spreading of competencies-based approach in HRM has led to replace specific and behavioral dimensions by broader competencies, probably again more complex and difficult to operationnalize. Even if they benefit from good face validity among human resources managers, these competencies-based assessment centers still have to demonstrate their construct-related and criterion-related validity. The purpose of the present study is to examine the construct-related and criterion-related validity of the assessment centre used to select entry-level candidates to the Belgian federal police force. Following a preseletion on the basis of a cognitive ability test, this assessment center taps seven competecies by using five techniques: a personnality inventory, two group simulations, an individual inteview and an interview by a jury. Data were obtained from 369 police officers which were selected in 2006 and which completed their traineeship one year later. As criteria of work performance, we used six training results: 4 scores of success in various achievement tests and two trainee’s behavioural evaluation by a trainer and by a professionnal tutor. Construct-related validity was tested by using a principal component analysis and a multitraits-multimethods matrix. Results confirm a well-known effect of common variance due to the method/technique. As regards criterion-related validity, we compared the respective predictive validity of two sets of predictors (competencies scores measured through different techniques versus global scores from each technique), controlling for cognitive ability score. Results show a low incremental predictive validity of assessment center scores over cognitive score but are in line with predictive values reported in similar studies. Several methodological and conceptual explanations were proposed to discuss these relatively disappointing results and to suggest future avenues for testing and improving validity of competencies-based assessment centers

Physiologic Determinants of Exercise Capacity in Pulmonary Langerhans Cell Histiocytosis: A Multidimensional Analysis

International audienceBackgroundReduced exercise capacity severely impacts quality of life in pulmonary Langerhans cell histiocytosis. Ascertaining mechanisms that impair exercise capacity is necessary to identify targets for symptomatic treatments.MethodsDyspnea, pulmonary function tests and cardiopulmonary exercise test were analysed in 62 study participants. Data were compared between subjects with impaired and normal aerobic capacity (V’O2 peak less than 84% versus 84% predicted or more). Data were reduced using a principal component analysis. Multivariate analysis included V’O2 peak as the dependent variable and principal components as covariates.ResultsV’O2 peak was reduced in 44 subjects (71%). Subjects with impaired aerobic capacity presented: (i) decreased FEV1, FVC, FEV1/FVC, DLCO and DLCO/VA and increased AaDO2, (ii) increased ventilatory equivalents at ventilatory threshold, VD/VT peak, AaDO2 peak and PaCO2 peak and decreased ventilatory reserve and PaO2 peak. There was no difference between groups in dyspnea scores. Principal component analysis extracted 4 principal components interpreted as follows: PC1: gas exchange; PC2: “pseudorestriction”; PC3: exercise-induced hyperpnea; PC4: air trapping. Multivariate analysis explained 65% of V’O2 peak. The 4 principal components were independently associated with V’O2 peak (βcoefficients: PC1: 9.3 [4.6; 14], PC2: 7.5 [3; 11.9], PC3: -5.3 [-9.6;-1.], PC4: -9.8 [-14,9;-4.7]).ConclusionImpaired exercise capacity is frequent in pulmonary Langerhans cell histiocytosis. It is mainly caused by pulmonary changes but is not associated with increased dyspnea intensity. Therefore, treating the lung represents a relevant approach for improving exercise capacity, even in patients experiencing mild dyspnea

Pulmonary function tests and incremental cycle exercise results.

<p>Pulmonary function tests and incremental cycle exercise results.</p

Correlations between the four principal components and CPET and PFT variables, n = 45.

<p>Correlations between the four principal components and CPET and PFT variables, n = 45.</p

Variables statistically correlated with V’O₂ peak.

<p>Variables statistically correlated with V’O₂ peak.</p