Impact of thresholding techniques on X-ray soil microtomogram analyses

in Geophysical Research Abstracts (2011), 13

Using X-ray microtomography, 3D soil structure can be visualised and analysed through useful factors like pore size distribution, shape, connectivity, orientation, etc. X-ray scans yield grey-level 2D ... [more ▼]

Using X-ray microtomography, 3D soil structure can be visualised and analysed through useful factors like pore size distribution, shape, connectivity, orientation, etc. X-ray scans yield grey-level 2D images, which can be recombined to form 3D structures. Treatments of the grey-level images can consist of either a binarization -distinguishing soil and pores- or a permeability level attribution directly linked to the grey-level values. The latter leads to problems in order to assign a permeability for each point (in soil a same grey level value can be assigned to points with a different permeability), as well as to analyse the 3D structure. On the other hand, treatment of black and white 3D structures is well-handled. However, the impact of the choice of one thresholding technique on the resulting images has already been demonstrated. Moreover, thresholding methods are various and numerous. Many of them are based on the image histogram analysis. But because of the soil complexity, the relevance of these techniques becomes debatable, with a risk of producing non reliable images. We propose to palliate this with a simple new algorithm based on physical measurements: it uses a loop fixing the threshold value in order to match the measured porosity for each sample. In this communication, our point is to highlight the impact of different thresholding techniques on the analysis and interpretation of our soil microtomograms. The underlying questions could be: Does the thresholding method influence our conclusions? Are the results depending on the sample itself or on the methodology? In order to answer these questions we tested the Otsu technique and our physically based algorithm. Soils samples were removed from the upper layer (Ap horizon) of a silty soil (Gentinnes, Brabant Walloon, Belgium) in plots with different management practices. In fact, since 2004, the field has been cultivated in conventional tillage (CT) or reduced tillage (RT). In order to empty the meso- and macroporosity, samples were placed under a 1.5 MPa pressure (Richards apparatus). Samples were then scanned by X-ray microtomography using a Skyscan-1172 high-resolution desktop micro-CT system (Skyscan, Kontich, Belgium). The cone beam source operated at 100 kV, using an aluminium filter. The detector configuration, i.e. 1048x2000 pixels with a 16-bit X-ray camera, and the distance source-object-camera were adjusted to produce images with a pixel size of 17 µm. Porosity was measured for each scanned sample. Then the threshold methods -the Otsu technique on one hand and our developed algorithm on the other - were applied, and morphological factors were calculated for both methods. A comparison of the first results shows a threshold influence on average porosity and number of pores, but also on connectivity factors and size distribution. The apparent porosity of the images, as well as connectivity, is underestimated with the Otsu technique. Despite the fact that the changes induced by thresholding are more important for RT than CT, global conclusions about the comparison of these agricultural practices are approximately the same in this case. However, differences between tillage systems are less important with the Otsu method, confirming the impact of choosing the adapted threshold method. [less ▲]

Impact of training and exercise intensity on blood antioxidant markers in healthy Standardbred horses

in Equine & Comparative Exercise Physiology (2004), 1(3), 211-220

This study investigated the effect of training and exercise intensity on blood antioxidant markers in six healthy Standardbred horses. Markers studied were uric acid (UA), ascorbic acid (AA), α-tocopherol ... [more ▼]

This study investigated the effect of training and exercise intensity on blood antioxidant markers in six healthy Standardbred horses. Markers studied were uric acid (UA), ascorbic acid (AA), α-tocopherol, vitamin A (Vit A), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione – reduced (GSH) and oxidized (GSSG), glutathione redox ratio (GRR), copper (Cu), zinc (Zn) and selenium (Se). The horses performed a standardized exercise test (SET) when they were untrained (T0), after 4 weeks of light training (T4) and after 8 weeks of interval training (T12). Forty-eight hours after SET T4 and SET T12, a SET with run up to fatigue (TTF4 and TTF12) was performed. Maximal oxygen consumption (V˙O2max) was determined within 3–5 days after TTF4 and TTF12. At each test (SET T(i) and TTF(i)), venous blood was sampled at rest (R), peak-exercise (Emax), 15 (E15) and 60 (E60) min after the test. UA, AA and GRR were increased significantly by the exercise, whereas GSH and Vit A were decreased significantly (P<0.05). Training-related increases (T0 vs. T4 vs. T12) were observed for UA, SOD, GPx and Se, whereas GSH, α-tocopherol and Zn decreased (P<0.05). Exercise intensity (TTF(i) vs. T(i)) increased UA and AA significantly and decreased GSH significantly (P<0.05). A significant correlation between ΔSOD and ΔV˙O2max (r=0.86, p<0.05) determined at SET T4 and SET T12 was found. Taken together, these results indicate that training and exercise intensity significantly influence blood antioxidant markers in healthy Standardbred horses [less ▲]

The impact of translated tests on student' performances

Conference (2006, July)

Impact of Transport and Dynamical Processes Upon Stellar Oscillation Frequencies

in EAS Publications Series (2007)

In order to prepare the theoretical interpretation of the oscillation frequencies detected by CoRoT, comparisons of results from standard stellar models by the ESTA group have proven to be very useful ... [more ▼]

In order to prepare the theoretical interpretation of the oscillation frequencies detected by CoRoT, comparisons of results from standard stellar models by the ESTA group have proven to be very useful. The next issue which is briefly addressed here is ``what are the additional physical processes that must be included in stellar models computed with different evolutionary codes for the next comparison exercises?'' We therefore discuss the impact on oscillation frequencies of several physical processes which are still poorly understood and/or poorly modelled but cannot be fully discarded. [less ▲]

Impact of uncertainty in climate forcing on projections of the West Antarctic ice sheet over the 21st and 22nd centuries

E-print/Working paper (2013)

Impact of visual modality on acoustic assessment of rooms

Poster (2011, May 27)

In the context of the conception of a multimodal immersive environment aimed to support the task of assessing the acoustical quality of rooms based on numerical simulations, we study the relationship ... [more ▼]

In the context of the conception of a multimodal immersive environment aimed to support the task of assessing the acoustical quality of rooms based on numerical simulations, we study the relationship between image and sound. Auralias project aims to develop an immersive environment for a collaborative work between architects and acousticians combining 3D sound rendering and 3D view of the room model. In this study, we analyzed the impact of a room picture on the acoustic assessment. We chose reverberation as acoustic parameter. First, we confronted 70 subjects with a sound clip and asked them to assess the reverberation degree (control condition). Then, we divided the subjects into three groups and repeated the same judgment task. However, in the first group, subjects listening the sound clip were confronted with a room picture consistent with the sound. In the second group, they were confronted with a « distractor » room picture (no link with the sound). In the last group, they listened the sound clip without any room picture. Our results showed a positive impact of consistent pictures on reverberation assessment but we found no effect of distractor pictures. [less ▲]

Impact of vocal load during a prolonged reading task with specific emphasis on the output level

Conference (2010, October 18)

La charge vocale se définit comme la quantité d'utilisation vocale en termes de durée et d'intensité vocale. Dans cette étude, nous tentons d'étudier la charge vocale selon ces deux aspects. Pour ce faire ... [more ▼]

La charge vocale se définit comme la quantité d'utilisation vocale en termes de durée et d'intensité vocale. Dans cette étude, nous tentons d'étudier la charge vocale selon ces deux aspects. Pour ce faire, nous avons proposé une tâche de lecture à 50 femmes non fumeuses, âgées de 22 à 47 ans, chez qui l'examen phoniatrique a exclu la présence de toute pathologie vocale. L'impact de la durée de l'utilisation vocale a été étudié à l'aide de récoltes de mesures toutes les 30 minutes, au cours d'une lecture de deux heures. Nous avons réalisé des mesures objectives (Fréquence fondamentale, Jitter %, Shimmer %, Noise-to-Harmonic Ratio, étendue fréquentielle, dynamique d'intensité, temps maximum de phonation) ainsi qu'une auto évaluation sur une échelle visuelle analogique (qualité vocale, sensation d'effort, de fatigue et d'inconfort laryngé au cours de la lecture). Afin de mettre en évidence l'effet de l'intensité, chaque participante a réalisé deux fois la tâche de deux heures de lecture, à minimum trois jours d'intervalle afin de permettre la récupération entre les deux conditions de test. Une première fois à intensité conversationnelle (entre 60 et 65 dB), une seconde fois à intensité élevée (entre 70 et 75 dB). L'objectif était d'étudier les modifications liées à la durée et à l'intensité de l'utilisation vocale ainsi que l'impact de l'échauffement et de la fatigue vocale sur les paramètres étudiés. [less ▲]

Impact of work on health

in Vandenbrande, T; Vandekerckhove, S; Vendramin, P (Eds.) et al Quality of work and employment in Belgium (2012)

Impact physiologique et pathologique du stress oxydant chez le cheval

in Annales de Médecine Vétérinaire (2005), 149(1), 1-9

Oxidative stress has become of increasing interest in research and in equine and human medicine. If the pro-oxidant burden overwhelms the endogenous antioxidant defence of the organism, the arising ... [more ▼]

Oxidative stress has become of increasing interest in research and in equine and human medicine. If the pro-oxidant burden overwhelms the endogenous antioxidant defence of the organism, the arising imbalance between pro- and antioxidants is defined as oxidative stress. Different pathways might increase the generation of reactive oxygen species ( ROS) and results in oxidative stress. In physiological conditions, like during moderated exercise, the balance between ROS production and antioxidants allows to maintain an optimal organic function. In the light of the potentially deleterious role of excessive ROS production and the evidence that exercise-induced oxidative stress occurs in horses, the assessment of the antioxidant status should be considered in sport horses. Recent researches indicate that oxidative stress may play a role in physiopathology of several pathological syndromes in horses. Therefore, with classical treatment, the controlled administration of antioxidants appears interesting for the modulation of these processes, as well as in sport horses during intense exercise period. [less ▲]

Impact studies and water management with WolfHydro : a new physically based hydrological solver

in International Symposium on Environmental Hydraulics (2001, December)