Browsing by Author "Velez, Maria"

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Open Access
Cretaceous Amber: A New Source of Bird Remains and of Palaeoecological Information in Dinosaur Bonebeds
(Faculty of Graduate Studies and Research, University of Regina, 2021-04) Cockx, Pierre Francois Dominique; Somers, Christopher; McKellar, Ryan; Velez, Maria; Finlay, Kerri; Hall, Britt
In order to reconstruct Cretaceous ecology and environments, this thesis investigates amber deposits in Myanmar and Western Canada, through chemical analyses of amber and study of the inclusions. As part of this work, I described a bird foot and a large series of feather inclusions from the amber of Myanmar. In the bird specimen, a series of osteological features and the morphology of the claws, support a systematic placement among Enantiornithes. I was able to describe delicate integumentary structures associated with the foot. This included scutellate scale feathers, a type of feather that has only been documented in Burmese amber specimens. Their distribution and relative size on the longest digit of the foot suggest a mechanosensory tactile function, and may allow us to draw parallels to some modern birds with tactile feathers on their feet. This finding strongly supports the longest digit acting as part of the feeding strategy of the bird, and fits well with previous interpretations of habitat use by enantiornithines. This dissertation demonstrates that even isolated vertebrate remains in amber are of high scientific interest. Through a detailed study of more than 180 Burmese amber samples preserving feathers, a diverse assemblage of Cretaceous feathers has been recovered. This provides the opportunity to document and investigate several structural types of feathers, ontogenetic stages, and pigmentation patterns. Based on recent work that associates feather types with skeletal remains, I was able to attribute many of the feathers to putative source animals. Although a few feathers may belong to non-avian dinosaur taxa, this survey confirmed earlier hypotheses that Enantiornithes were the dominant source of feathers in this ecosystem. The structure and pigmentation patterns reported added to larger-scale hypotheses regarding the groups present in the Cretaceous amber forest. One particular subset of ornamental feathers warranted detailed study because of its unusual structure. I determined that rachis-dominated feathers (RDFs) form a distinct morphotype characterized by a ventrally open rachis and a flexibility that was not documented previously. These results allow us to refine our evolutionary-developmental (evo-devo) models for integumentary structures in dinosaurs by providing additional data on structures preceding modern feathers. The structural features observed support a particular pathway for evolutionary development in feather subcomponents, addressing a major question in evo-devo models of feathers which have been based predominantly on modern material. A research deficit was addressed by focusing on Upper Cretaceous bonebed amber deposits of Western Canada. I established that amber can provide paleoecological, paleoenvironmental, paleoclimatic, and paleogeographic data, thus improving our knowledge of dinosaur habitats and their biota. Stable isotope analyses of amber refined our knowledge of the actual position and extant of the Western Interior Seaway (WIS) during the Late Cretaceous. A marine signal indicates the presence of remnants of the WIS near the deposits studied. Fourier-transform Infrared spectra showed that the dominant tree in the forests belonged to the Cupressaceae group. Feather fragments in Pipestone Creek amber, reveal the presence of aquatic birds (e.g., Hesperornithes and Ichthyornithes) 73 Ma, in Pachyrhinosaurus habitats. Insect inclusions yielded new species of Mymarommatidae wasp and Psocoptera which add to the fossil record and support the ecological interpretations based on amber chemistry. Ultimately, this line of research further supports paleoenvironmental hypotheses based on other sources of data. It also provided a new source of information on Cretaceous terrestrial habitats at high latitude, and a source for comparisons to other amber deposits during the latter part of the Cretaceous.
Open Access
A Deep Learning Based Approach for Canola and Weed Segmentation in Precision Agriculture
(Faculty of Graduate Studies and Research, University of Regina, 2021-08) Sami Ullah, Hafiz; Bais, Abdul; Paranjape, Raman; Velez, Maria; Yow, Kin-Choong
Weeds are unwanted plants that can be eliminated using herbicides. Traditionally, these herbicides are sprayed uniformly which consumes an unnecessary amount and leaves adverse e ects on the environment. We can signi cantly cut this usage by selective spraying. It can be achieved using a decision map produced using eld images. Firstly, for all the images, classi cation is performed at the pixel level in either crop or weed. Then, the percentage of each class is calculated. Finally, these percentages are mapped using Global Positioning System (GPS) locations to generate a nal decision map for selective spraying. This thesis focuses on the classi cation part of the plants at a pixel level. Currently available models are not suitable as they need more storage. We aim for model optimization without performance loss. To accomplish this objective, we start with preparing data. We use Maximum Likelihood Classi cation (MLC) and image processing techniques to label eld images in three classes: background, crop, and weeds. Then, we use ResNet-50 based U-Net like classic architecture and modify it to reduce the number of parameters. In the modi cation we convert the normal convolution into two sub operations: point-wise and depth-wise convolution. This optimization drops the performance which we maintained by introducing the rich low-level features. The variety in low level features is achieved with the help of a parallel feature extraction module which uses dilated lters. Dilated lter requires a small number of parameters to extract a bigger picture and connectivity of the features. In other words, a small kernel is used to approximate a large size kernel. The result is an improvement in semantic accuracy with reduced memory requirement. While training the model, we include data diversity using image augmentation. It also helps solve challenges in the dataset. With extensive experiments over objective function, we choose DICE loss to train the model which provides solution to the data imbalance problem. A comparison is made for quantitative and qualitative analysis with state-of-the-art. We achieve 89.18% mean Intersection Over Union (mIOU) with 86.33%, 83.19%, and 98.01% individual IOU for the crop, weeds, and background, respectively. We also use Average Precision (AP) to report numerical results. Our proposed model is more con dent in classifying weed and background with a score of 92.83% and 99.57%, respectively. Overall, our proposed methodology reports mAP 95.54%, 0.7% more than HRNet MScale. In terms of memory requirement, our proposed model uses only 15M parameters which are 57M less than the state-of-the-art models with a compromise of 1% mIOU score. It only requires 60 Megabytes (MB) of storage which is 10 less than HRNet MScale.
Open Access
Dewatering Behaviour of Clay Slurries
(Faculty of Graduate Studies and Research, University of Regina, 2017-01) Khan, Faseel Suleman; Azam, Shahid; deMontigny, David; Velez, Maria; Huang, Gordon
The main objective of this research was to develop a fundamental understanding of the dewatering behaviour of clay slurries. A comprehensive research methodology was developed to understand the natural dewatering processes of consolidation, desiccation and consolidation-desiccation. Laboratory investigation methods were improved, data analysis techniques were enhanced, and numerical methods were customized. An active clay slurry was prepared at different initial conditions (3 LL to 1 LL) to mimic field conditions ranging from a thin slurry to a paste-like consistency. Thin samples were used in a conventional oedometer test and in the evaporation test. A correlation was developed between the oedometer test and the bench-top centrifuge test to describe slurry consolidation. Likewise, the instantaneous profile method was applied to thin samples resulting in avoiding the need of instrumentation in evaporation tests. The small-strain consolidation theory was customized to predict large-strain consolidation deformations and diffusion equation was used to simulate desiccation. The use of effective stress and soil suction as state variables was found suitable for clay slurries. A consolidation-desiccation framework was developed to identify the governing dewatering processes operative within a slurry deposit. This research produced useful laboratory test methods, which can be implemented at on-site laboratories for determining the consolidation and desiccation properties of clay slurries. Similarly, the improved understanding of the significance of initial conditions (suspension to a paste-like consistency) on slurry dewatering is important to develop material-specific tailings deposition schemes. Finally, an understanding of the governing dewatering processes is useful to develop site-specific tailings management strategies.
Open Access
Representations of McLain Groups
(Faculty of Graduate Studies and Research, University of Regina, 2016-06) Izadi, Mohammadali; Szechtman, Fernando; Herman, Allen; Velez, Maria; Gilligan, Bruce; Garcia, Gaston
Basic modules of McLain groups are defined and investigated. These are a (possibly infinite dimensional) generalization of Andre’s basic modules of the multiplicative group of upper triangular square matrices over a finite field with 1’s on the main diagonal. The ring R need not be finite or commutative and modules of a McLain group are allowed to be infinite dimensional over an arbitrary field F. The set , totally ordered by , is allowed to be infinite. We show that distinct basic modules are disjoint, determine the dimension of the endomorphism algebra of a basic module, find when a basic module is irreducible, and we study the problem of finding a decomposition of a basic module as direct sum of irreducible submodules.
Open Access
Stratigraphic Investigations into the Genesis of Anomalously Thick Coal Deposits in East-Central Saskatchewan
(Faculty of Graduate Studies and Research, University of Regina, 2016-09-07) Berenyi, Jason Ashley; Qing, Hairuo; Velez, Maria
The discovery of anonymously thick Cretaceous-age coal deposits in east-central Saskatchewan in 2008 generated a great deal of interest in the province and raised a number of geologic questions. Unlike other parts of the Saskatchewan where Mannville coals are laterally extensive and restricted to a few metres of thickness, these deposits appeared to be hosted in isolated ‘sub-basins’ with coal thicknesses exceeding 100 m. Coal accumulating in these thicknesses is exceptionally rare, comprising less than 1% of global deposits. The remarkable nature of these deposits provided the impetus for this study, with the aim of unravelling the geologic processes responsible for their development. A reconstruction of the depositional history in east-central Saskatchewan, within the context of the development of the Western Canada Sedimentary Basin, showed that the study area was subject to a unique mixture of marginal marine and terrestrial sedimentary environments at various stages through the Devonian to Cretaceous periods. These settings exposed the project area to a number of geologic processes that facilitated the development of these coal deposits. Seventeen separate deposits have been discovered in the study area, and are delineated by over 140 drillholes. Detailed logging was conducted on 103 of these drillholes and the results were used to correlate the lithologic units with documented regional stratigraphy. Stratigraphic correlations across the sub-basins revealed abrupt changes in elevations of Paleozoic strata, over horizontal distances of less than 100 m. These changes reflect paleotopographic lows which appear to have developed on the Paleozoic carbonates by karsting or erosion, or a combination of the two.
Open Access
Utilizing amber isotope geochemistry to understand anomalous dinosaur diets
(2024-11-06) Egan, Ben, M.J.; Velez, Maria; McKellar, Ryan, C.