Control of fault geometry, interaction and mechanical stratigraphy on strain distribution in normal fault zones

It is known that the development and distribution of strain associated with normal faulting is influenced by the process of fault growth within mechanically layered and heterogeneous sedimentary rocks. Fault displacement is often partitioned between discontinuous throw on slip surfaces and zones of distributed strain, which in some cases can be the result of folding associated with normal faulting. The amount of ductile deformation can vary significantly along the strike of a normal fault array as a result of various processes, such as fault-tip propagation and fault interaction and linkage. In this study we investigate the influence of mechanical stratigraphy, fault geometry and fault mechanical interaction on the variability and distribution of ductile strain in the rock volume surrounding normal faults. We show that mechanical competence contrasts can control the manner in which strain is accommodated and, hence the overall patterns of secondary fault and fracture systems within normal fault-related folds. This can have consequences on the way in which disruption of an associated shale smear occurs, impacting the sealing properties of the fault zones. Also, we show that folding can be generated by different mechanisms that vary in importance in time and space along a normal fault array. Mechanical properties of the host rocks, together with the spatial configuration of the faults control the mechanical interaction between faults, exerting an influence on the variability of ductile strain within the volume of deformation surrounding normal faults. Specifically, conjugate normal faults that intersect within layers with low compressibility have geomechanical characteristics favorable for migration of stress concentrations near the upper fault tips which generate higher propagation/slip ratios and the development of lower amplitude folds, or no folding. The host rock lithology and the overlapping normal fault configuration at the time of interaction controls the three-dimensional relay ramp geometries and associated strains within relay ramps. Normal faults within mechanically competent rocks tend to develop relay ramps with tabular geometries, that have larger aspect ratios and smaller fault-parallel shear strains compared to those developed in mechanically incompetent rocks. Fault-normal shear strain within ramps can be the result of the development of asymmetric displacement gradients on the overlapping faults as a result of mechanical interaction between surface-breaking normal faults. The probability of a relay ramp bounded by surface-breaking normal faults to be completely breached depends not only on the accumulated ramp shear strains and the ratio between throw and separation of the bounding faults, but also on how the throw is partitioned between the interacting faults. Also, we argue that the style of breaching, dominantly through the upper part of the relay ramps, is influenced by the stress interaction between the overlapping faults and the Earth’s free surfac

Online Teaching: Creating Text-Based Environments for Collaborative Thinking

This article examines some of the ways graduate students engage in interactive writing in online university courses as a means of discussion. In particular I present data from course transcripts that suggest that discursive interaction in an asynchronous, text-based, online course may be uniquely suited to fostering higher-order thinking and social construction of meaning. I support this argument by considering the emergent online community and its participation structures, qualities of the interactive written discourse, and means by which the discourse supports making meaning and higher-order thinking. Findings support research that suggests that well-designed, text-based, online courses for university students create collaborative learning environments that enhance thinking.Cet article porte sur quelques-unes des façons dont les étudiants des deuxième et troisième cycles participent aux discussions interactives dans le cadre de cours universitaires en ligne. Nous y présentons des données tirées de relevés de notes et qui laissent croire que l'interaction discursive dans le contexte d'un cours en ligne asynchrone à base de textes peut s'avérer particulièrement apte à favoriser des processus mentaux de niveau élevé et la construction sociale de la signification. Pour appuyer ce point de vue, nous tenons compte de la communauté virtuelle naissante et de ses structures de participation d'une part et des qualités du discours interactif et des moyens par lesquels il appuie la construction de la signification et les processus mentaux de niveau élevé d'autre part. Les résultats viennent appuyer la recherche qui propose que les cours universitaires en ligne, bien conçus et à base de textes créent des environnements d'apprentissage collaboratif qui promeuvent la réflexion

Guest Editor\u27s Introduction: Teacher Research on Classroom Discourse in Northern Canadian Communities

This special issue brings together a series of articles written by practitioners in a number of northern communities in British Columbia, all of whom are affiliated with UNBC\u27s graduate program in Curriculum and Instruction. The region they are writing about is large, rugged, and sparsely populated. Prince George, centrally located and the site of the main UNBC campus, has a population of 75,000. There are seven other small cities in the 10,000-20,000 range, and the remainder of the population resides in small towns and villages

Electronic Payment Systems Development in a Developing Country: The Role of Institutional Arrangements

This paper examines the institutional arrangements in the development of Nigeria’s electronic payment system (EPS) using a new institutional economics (NIE) perspective. A case study of Nigeria’s EPS was carried out using semi structured interviews to collect data from 18 participating stakeholders; a thematic method was used for the data analysis. The study suggests that a well-functioning set of arrangements, which is lacking in the institutional setup in Nigeria may be required to build necessary institutional capacity suitable for development of safe and efficient electronic payment systems. Although the technological payment infrastructure in Nigeria is modern and of comparable standard, the failure to put in place reliable and relevant market and collaborative agreements has not enabled full exploitation of the available infrastructure. Current governance structures show elements of power struggle and distrust between stakeholders (players and regulators), hampering the creation of an environment that would sustain free market economic activities and effective development of payment systems

Student Reports in the Digital Age: An Invitation to Classroom Inquiry on Controlled Research

The digital age provides an overwhelming amount of information and an array of modes, including text, images, and sound, for presenting student learning. Without a comprehensive strategy for teaching information processing and presentation, student reports can be overwhelming for both students and teachers. The authors present research platforms as explicit instruction with potential to scaffold students toward multimodal literacy and purposeful independent inquiry presented with a confident voice. In research platforms, teachers create multimodal text sets on topics of interest and guide students to collect information, make sense of it, and present it to peers in engaging formats. Rather than advocate the research platform strategy as tested and true, the authors invite readers to join an electronic network, a virtual community of practice, to share text sets and reflect collaboratively on student responses. The authors expect to report developmentand evaluation of the strategy and of the network in subsequent articles

Canopy spectral reflectance detects oak wilt at the landscape scale using phylogenetic discrimination

The oak wilt disease caused by the invasive fungal pathogen Bretziella fagacearum is one of the greatest threats to oak-dominated forests across the Eastern United States. Accurate detection and monitoring over large areas are necessary for management activities to effectively mitigate and prevent the spread of oak wilt. Canopy spectral reflectance contains both phylogenetic and physiological information across the visible near-infrared (VNIR) and short-wave infrared (SWIR) ranges that can be used to identify diseased red oaks. We develop partial least square discriminant analysis (PLS-DA) models using airborne hyperspectral reflectance to detect diseased canopies and assess the importance of VNIR, SWIR, phylogeny, and physiology for oak wilt detection. We achieve high accuracy through a three-step phylogenetic process in which we first distinguish oaks from other species (90% accuracy), then red oaks from white oaks (Quercus macrocarpa) (93% accuracy), and, lastly, infected from non-infected trees (80% accuracy). Including SWIR wavelengths increased model accuracy by ca. 20% relative to models based on VIS-NIR wavelengths alone; using a phylogenetic approach also increased model accuracy by ca. 20% over a single-step classification. SWIR wavelengths include spectral information important in differentiating red oaks from other species and in distinguishing diseased red oaks from healthy red oaks. We determined the most important wavelengths to identify oak species, red oaks, and diseased red oaks. We also demonstrated that several multispectral indices associated with physiological decline can detect differences between healthy and diseased trees. The wavelengths in these indices also tended to be among the most important wavelengths for disease detection within PLS-DA models, indicating a convergence of the methods. Indices were most significant for detecting oak wilt during late August, especially those associated with canopy photosynthetic activity and water status. Our study suggests that coupling phylogenetics, physiology, and canopy spectral reflectance provides an interdisciplinary and comprehensive approach that enables detection of forest diseases at large scales. These results have potential for direct application by forest managers for detection to initiate actions to mitigate the disease and prevent pathogen spread

Quantitative evaluation of fatty liver using spectroscopic sequence – correlation between Magnetic Resonance Spectroscopy and histopathology

Department of Radiology and Medical Imaging, University of Medicine and Pharmacy of Craiova, Craiova, Romania, The IVth Congress of Radiology and Medical Imaging of the Republic of Moldova with international participation, Chisinau, May 31 – June 2, 2018Introduction: La stéatose hépatique entraîne l’accumulation des lipides dans les hépatocytes. La tomographie computerisée (CT) et l’échographie (US) peuvent évaluer qualitativement la graisse du foie. La technique d’imagerie la plus précise en termes de quantification de la stéatose hépatique est la Spectroscopie par Résonance Magnétique (MRS). L’objectif de l’étude était de valider le rôle de MRS 3T dans l’évaluation quantitative de la stéatose hépatique. Matériel et méthodes: Le foie de 33 patients a été évalué qualitativement par des tests de laboratoire et d’échographie. Tous les patients ont été étudiés avec une 3T haute résolution IRM, constituée de séquences en phase, déphasées et de séquences spécifiques pour la steatose en T1 pondérées, ainsi que des séquences en T2 pondérées et de séquences de spectroscopie. L’évaluation qualitative a été réalisée en utilisant la fraction de graisse calculée manuellement après l’analyse par spectroscopie. La stéatose a été classée 0 = jusqu’à 10%, grade 1 = 10-33%, grade 2 = 34-66%, grade 3 = ≥67%. La biopsie hépatique a été réalisée chez des patients opérés pour différentes pathologies. Résultats: Limitée par un petit nombre de patients et par les manoeuvres chirurgicales invasives de la biopsie hépatique, l’étude montre que cinq patients présentaient une stéatose classée en grade 0, treize – en grade 1, six – en grade 2 et un – en grade 3, offrant une bonne corrélation entre MRS et histopathologie. Conclusions: En dépit d’être une étude pilote, nous pouvons conclure que MRS est une technique non invasive efficace qui peut être extrêmement utile dans le diagnostic et la quantification de la stéatose hépatique.Background: Hepatic steatosis results in the accumulation of lipids within hepatocytes. Computed Tomography (CT) and Ultrasound (US) can qualitatively assess liver fat. The most accurate imaging technique in terms of quantifying hepatic steatosis is Magnetic Resonance Spectroscopy (MRS). The study aimed to validate the role of 3T MRS in quantitative assessment of liver steatosis. Material and methods: The liver of 33 patients was qualitatively assessed through lab and ultrasound tests. All patients were investigated with a 3T high resolution MRI consisting of T1 weighted sequences with in-phase, out-of-phase and fat specific phases and also T2 weighted and spectroscopy sequences. The qualitative assessment was carried out using the fat fraction calculated manually after spectroscopy computer analysis. The steatosis was graded as grade 0 = up to 10%, grade 1 = 10-33%, grade 2 = 34-66%, grade 3 = ≥ 67%. Liver biopsy was performed in patients who underwent surgery for different pathologies. Results: Limited by a small number of patients and surgical invasiveness of liver biopsy, the study shows that five patients had grade 0 steatosis, thirteen had grade 1, six patients – grade 2 and one patient – grade 3, offering a good correlation between MRS and histopathology. Conclusions: Despite being a pilot study, we can conclude that MRS is an effective noninvasive technique that can be extremely useful in diagnosing and quantifying hepatic steatosis