Détermination de la conductivité hydraulique à saturation d'un sol non saturé par suivi d'infiltration à l'aide de la tomographie de résistivité électrique

RÉSUMÉ Nous présentons le développement d'une nouvelle méthodologie qui permet d'estimer la conductivité hydraulique à saturation en utilisant la tomographie de résistivité électrique lors d'un suivi d'infiltration dans un sol non-saturé ainsi que le développement d'une nouvelle méthode de maillage pour le problème d’inversion en tomographie de résistivité électrique. Cette thèse inclut deux articles qui ont été soumis dans des revues scientifiques reconnues internationalement----------ABSTRACT We present the development of a new methodology to estimate the saturated hydraulic conductivity using electrical resistivity tomography to monitor water infiltration in an unsaturated soil, and the development of a new intelligent meshing technique for electrical resistivity tomography inversion problems. This thesis includes two articles that were submitted to international refereed scientific journals

Magnetotelluric prospecting in the Matagami mining camp

RÉSUMÉ Dans ce mémoire, un logiciel de modélisation 2D MT a été modifié afin d’y inclure une résistivité complexe variant en fonction de la fréquence suivant une équation Cole-Cole. Ce nouveau logiciel a été validé à l’aide de solutions analytiques et certains résultats publiés de modèles 2D incluant des effets de dispersion. Les réponses calculées de modèles présentant des effets de dispersion ont la possibilité d'être détectées mais seulement pour des corps situés à une profondeur inférieure à leurs dimensions. Les propriétés électriques (i.e. résistivité, chargeabilité, constante de temps) et les dimensions du corps influencent grandement les réponses MT et l’habilité d'être detectés par la méthode MT. La possibilité d’imager des structures dans le camp de Matagami a été examinée par le moyen de modélisation et d’interprétation des sondages MT éxistants. La présence de distorsion et de bruit dans les données a été mise en évidence dans les sondages MT. Plusieurs méthodes ont été utilisées pour déterminer la dimension du sous-sol localisé sous la région sondée par la MT. Ces méthodes démontrent que la région se trouve entre 2D/3D et 3D. Des inversions 2D ont été effectuées pour les profils MT et les pseudo-profils (profils perpendiculaires aux profils MT). On en déduit que le milieu contient des structures 2D de toutes tailles, dimension et orientation dans un milieu 3D. Les résultats des inversions 2D ont été interpolés pour construire un modèle 3D. Une modélisation 3D MT a été faite pour vérifier la qualité des inversions 2D dans un cas 3D. Le résultat a été satisfaisant pour les données MT dont les réponses MT modélisées ressemblent fortement aux sondages. En ajustant les couches profondes et en ajoutant les corrections des effets statiques, il est possible de reproduire des modèles qui ajustent beaucoup mieux les données MT.----------ABSTRACT In this thesis, 2D MT modeling program was modified to include a varying complex resistivity with frequency by implementing the Cole-Cole equation in the forward code. The code was validated with analytical solutions and some existing results to MT models with resistivity dispersion. Bodies with induced polarization (IP) effects were found to be detectable but only for bodies at depths less than their geometrical dimensions. The electrical and inductive properties (i.e. chargeability (m), time constant (τ) ...) of the body greatly influence the outcome of the MT response and the ability to be detected by the MT. The capability of mapping structures in the Matagami mining camp was investigated by modelling and by interpretation of a very large existing MT survey. Strong presence of distortion and noises were found in the magnetotelluric (MT) survey data at the Matagami southern flank region. Various methods were used to quantify the dimensionality of the surveyed region as 2D/3D and 3D. 2D inversion was done parrallel and perpendicular to the determined strike direction. We have found the MT surveyed area to contain 2D medium size structures of mixed size, orientation and shape in a 3D medium. The inversion results were then interpolated to build a 3D model. 3D forward response was done to verify the fit of the 3D model responses with the survey data. The 3D model responses resemble the survey data. By adjusting the 1D earth crust model and by adding a static shift correction, it is possible to produce responses that better fit the survey data

High levels of serum macrophage migration inhibitory factor and interleukin 10 are associated with a rapidly fatal outcome in patients with severe sepsis

SummaryObjectivesThe aim of this study was to delineate the association between high macrophage migration inhibitory factor (MIF) and interleukin 10 (IL-10) levels in the early phase of sepsis and rapidly fatal outcome.MethodsOne hundred and fifty-three adult subjects with the main diagnosis of severe sepsis (including septic shock) admitted directly from the emergency department of two tertiary medical centers and one regional teaching hospital between January 2009 and December 2011, were included prospectively. MIF and IL-10 levels were measured and outcomes were analyzed by Cox regression analysis according to the following outcomes: rapidly fatal outcome (RFO, death within 48h), late fatal outcome (LFO, death between 48h and 28 days), and survival at 28 days.ResultsAmong the three outcome groups, IL-10 levels were significantly higher in the RFO group (p < 0.001) and no significant differences were seen between the LFO and survivor groups. After Cox regression analysis, each incremental elevation of 1000 pg/ml in both IL-10 and MIF was independently associated with RFO in patients with severe sepsis. Each incremental elevation of 1000 pg/ml in IL-10 increased the RFO risk by a factor of 1.312 (95% confidence interval 1.094–1.575; p=0.003); this was the most significant factor leading to RFO in patients with severe sepsis.ConclusionsPatients with RFO exhibited simultaneously high MIF and IL-10 levels in the early phase of severe sepsis. Incremental increases in both IL-10 and MIF levels were associated with RFO in this patient group, and of the two, IL-10 was the most significant factor linked to RFO

Intelligent meshing technique for 2D resistivity inverse problems

In geophysical inverse problems, an a priori structured mesh is often used for inversion and mesh refinement is applied if needed by the user after observation of inversion results. We have developed a new intelligent self-adaptive unstructured finite-element meshing technique for electrical resistivity tomography inverse problems. This new approach uses Harris corner-and-edge detectors that are based on the local autocorrelation function of 2D distribution of pixels. This meshing technique optimizes the size of the inverse problem by refining areas where variations in the physical property structure are sensed to be important. The meshing technique also generates a more appropriate and optimum mesh for the inverse problem that is dependent on the problem itself. Tests on modeled data have demonstrated that the proposed intelligent meshing technique can reduce data misfit, produce a better reconstruction of the true physical properties, and minimize the size of the inverse problem. The synthetic model consists of a conductive dike in a resistive medium. By applying the proposed intelligent meshing technique, the inverse model of the dike is very similar to the inverse model produced using fine meshes, and it is also better reconstructed than the inverse model produced using conventional meshes. We have also applied the intelligent meshing technique to survey data collected for groundwater-saltwater mapping and characterizing the subsurface conductive structure with topography included. Our results indicate that the new meshing technique can produce solutions that are comparable with standard meshing and fine meshing techniques, while optimizing the size of the inverse problem.</jats:p

Motion Freeze for Respiration Motion Correction in PET/CT: A Preliminary Investigation with Lung Cancer Patient Data

Purpose. Respiratory motion presents significant challenges for accurate PET/CT. It often introduces apparent increase of lesion size, reduction of measured standardized uptake value (SUV), and the mismatch in PET/CT fusion images. In this study, we developed the motion freeze method to use 100% of the counts collected by recombining the counts acquired from all phases of gated PET data into a single 3D PET data, with correction of respiration by deformable image registration. Methods. Six patients with diagnosis of lung cancer confirmed by oncologists were recruited. PET/CT scans were performed with Discovery STE system. The 4D PET/CT with the Varian real-time position management for respiratory motion tracking was followed by a clinical 3D PET/CT scan procedure in the static mode. Motion freeze applies the deformation matrices calculated by optical flow method to generate a single 3D effective PET image using the data from all the 4D PET phases. Results. The increase in SUV and decrease in tumor size with motion freeze for all lesions compared to the results from 3D and 4D was observed in the preliminary data of lung cancer patients. In addition, motion freeze substantially reduced tumor mismatch between the CT image and the corresponding PET images. Conclusion. Motion freeze integrating 100% of the PET counts has the potential to eliminate the influences induced by respiratory motion in PET data

Prevalence of workplace violent episodes experienced by nurses in acute psychiatric settings

Nurses who experience workplace violence exhibit compromised care quality and decreased work morale, which may increase their turnover rate. This study explored prevalence of workplace violence, the reaction of victims, and workplace strategies adopted to prevent violence among acute psychiatric settings in northern Taiwan. A cross-sectional study was conducted, which consisted of 429 nurses who completed the Chinese version of the Workplace Violence Survey Questionnaire developed by the International Labor Office, International Council of Nurses, World Health Organization, and Public Services International. The rates of physical and psychological violence were 55.7% and 82.1%, respectively. Most perpetrator of the workplace violence were patients. Most victims responded by instructing the perpetrator to stop, followed by narrating the incident to friends, family, and colleagues. Only 4.9%-12% of the victims completed an incident or accident form, and the main reason for not reporting these violent incidents was the belief that reporting such incidents was useless or unimportant. The major strategies adopted by workplaces to prevent violence were security measures, patient protocols, and training. Institutions should train staff to handle violence, provide a therapeutic environment, simplify the reporting process, and encourage reporting of all types of violence

Planning Lung Radiotherapy Incorporating Motion Freeze PET/CT Imaging

Motion Freeze (MF), which integrates 100% of the signal of each respiratory phase in four-dimensional positron emission tomography (4D-PET) images and creates the MF-PET, is capable of eliminate the influences induced by respiratory motion and dispersing from three-dimensional PET (3D-PET) and 4D-PET images. In this study, the effectiveness of respiratory gated radiotherapy applying MF-PET (MF-Plan) in lung cancer patient was investigated and compared with three-dimensional intensity modulated radiotherapy (3D-Plan) and routine respiratory gated radiotherapy (4D-Plan) on the impact of target volume and dosimetry. Thirteen lung cancer patients were enrolled. The internal target volumes were generated with 40% of maximum standardized uptake value. The 3D-Plan, 4D-Plan, and MF-Plan were created for each patient to study the radiation to the targets and organs at risk. MF-Plans were associated with significant reductions in lung, heart, and spinal cord doses. The median reductions in lung V20, lung mean, heart mean doses, and spinal cord maximum dose compared with 3D-Plans were improved. When compared with 4D-Plans, the median reductions in lung V20, lung mean dose, heart mean dose, and spinal cord maximum dose were improved. Our results indicate that the MF-Plan may improve critical organ sparing in the lung, heart, and spinal cord, while maintaining high target coverage