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Open Access
Bangladeshi English for Academic Purposes (EAP): novice and experienced teachers’ perspectives on written corrective feedback
(2024-07-11) Alam, Md Zahangir; De Oliveira Jayme, Bruno (Curriculum, Teaching and Learning); Honeyford, Michelle (Curriculum, Teaching and Learning); Morin, Francine
Abstract This study aimed to identify the factors that shape novice and experienced teachers’ beliefs about written corrective feedback and the factors that influence teachers’ practices with students’ writing in the Bangladeshi context. The study intended to: 1) provide in-depth data on writing teachers’ perspectives of written corrective feedback (WCF) and how those perspectives evolved; 2) clarify writing teachers’ feedback preferences and the factors that determine how they approach those specific techniques; 3) show the challenges instructors encounter in practicing written corrective feedback on students’ writing; and 4) identify factors influencing teachers’ WCF practices. The study’s findings demonstrate that teaching experience has a significant impact on shaping teachers’ beliefs about WCF practices because it gives instructors access to many additional influences, such as having attended more professional developments sessions and interacted with professionals within developed networks. Furthermore, teacher education programs and professional development sessions do not equally contribute to developing novice and experienced teachers’ beliefs, because new teachers have fewer professional development opportunities than experienced instructors. As students themselves, the experienced teachers received direct WCF on their papers—primarily on grammar problems—but they now provide indirect feedback on substance and structure to their own students. They adjusted their WCF practices over time as they gained teaching expertise. However, prior learning experience has a considerable impact on how new teachers form their attitudes about WCF. Institutional variables have a greater impact on new teachers’ WCF practices than on those of experienced ones. Moreover, the experienced group prefers to provide indirect WCF and focus on global issues of writing such as essay structure, whilst the novices prefer to provide direct feedback on local concerns such as sentence structure and spelling. Finally, instructional issues like class time and work pressure seem to be difficult for both beginner and experienced teachers, as they must balance class time and work pressure, though reluctance to provide adequate WCF has a divergent trend. However, institutional challenges are more prominent among new teachers. University administrators in Bangladesh, practicing writing instructors, and department heads of advanced teaching and learning centers may benefit from the outcomes of this study.
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Open Access
Assessment of mechanical properties and microstructure of Co-Cr dental alloys manufactured by casting, milling, and 3D printing
(2024-07-10) Schettini, Ana Cecília; Franca, Rodrigo (Restorative Dentistry); Solomon, Charlene (Restorative Dentistry); Pesun, Igor J.
Purpose The aim of the present study is to investigate the effect of the three different Co-Cr manufacturing processes on the mechanical properties and microstructure of Co-Cr dental alloys. Methods Dumbbell-shaped specimens (n=6) were fabricated with CAST (lost wax casting technique), CNC (computer numerical control milling), and DMLS (direct metal laser sintering) techniques. The mechanical propertied were evaluated following the (ISO) standard 6892. Tensile test was performed to evaluate 0.2% yield strength, tensile strength, elongation, and elastic modulus, 3- point-bending test was done for flexural strength, and microhardness test to analyze hardness. The microstructure was evaluated through scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), as well as X-ray diffraction analysis (XRD) for alloy phase identification. Statistical differences for the tensile test, 3-point-bending, and hardness were evaluated by oneway ANOVA followed by post hoc Tukey tests to determine the interaction among the groups. Results The DMLS groups showed the highest values for 0.2% yield strength (908.0±13.1MPa), tensile strength (1123.7±6.5MPa), flexural strength (2273.0±43.2MPa), and microhardness (438.2±44.9HV) followed by CAST (462.1±8.0MPa, 632.6±23.7MPa, 1351.2±35.7MPa, and 400.0±33.3HV respectively) and CNC (413.0±10.0MPa, 533.1±17.4MPa, 1155.6±41.7MPa, and 295.0±22.1 HV respectively). No statistical differences found for elongation between CNC (15.3±3.9%) and DMLS (10.1±0.6%), as well as for DMLS (10.1±0.6%) and CAST (2.3±0.2%) (P>.05). No statistical differences found for elastic modulus among all groups (P>.05). EDX 2 revealed a slightly different chemical composition among the groups. XRD spectra revealed facecentered cubic (fcc) as the dominant phase and a small amount of hexagonal close-packed (hcp) in all three tested groups, as well as a peak of σ phase identified exclusively in the CAST group. Conclusions The mechanical properties and microstructures of Co-Cr dental alloys is dependent on the fabrication method. Overall, DLMS specimens performed better than CAST and CNC.
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Open Access
Wettability of saliva substitutes on CAD/CAM denture base materials
(2024-06-26) Mikhail, Paul; Franca, Rodrigo (Restorative Dentistry); Azpiazu Flores, Francisco (Restorative Dentistry); Pesun, Igor
Purpose: To measure and compare contact angle (CA) goniometry of liquids on denture bases manufactured by different methods, and to investigate the impact of physical and chemical topography, as well as various saliva substitutes, on contact angle measurements. Methods: This study was organized into three phases. Phase 1 measured contact angle (CA) of deionized water on two non-polished CAD/CAM denture bases: Mnp (milled; Lucitone 199 disc milled in Dentsply MCX5) and Pnp (printed; Formlabs denture base resin printed in Formlabs 3B). Phase 2 measured CA of deionized water on 5 polished denture bases: C (conventional; Lucitone 199 heat cured), M (milled), P (printed), I (injection molded; Ivocap), and F (flexible; Ultraflex). Phase 3 measured CA of 5 saliva substitutes – Biotene, VEGA, Spry, Moi-Stir, and Dentilube – on the 5 polished denture bases. Ten droplet measurements were obtained for each group, with each droplet analyzed for static CA, advancing contact angle (ACA), receding contact angle (RCA), and contact angle hysteresis (CAH). Statistical analysis was conducted using ANOVA, with a significance level set at 0.05. Results: The Pnp exhibited the highest ACA with statistical significance, while the Pnp, Mnp, and I had the lowest RCA. CAH was demonstrated to have statistically significant differences among the denture bases, with Pnp exhibiting the largest CAH, followed by Mnp, and then the polished denture bases. There were no significant differences in CAH among the polished denture bases. The saliva substitutes exhibited differences in ACA, with Spry and VEGA having the highest ACA, while Biotene had the lowest. Conclusion: The manufacturing methods of denture bases influences the CAH, while the chemical composition of the denture base specimens does not appear to affect CAH. Saliva substitutes do, however, impact CA measurements.
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Open Access
The effect of exclusive breastfeeding, exclusive bottle-feeding, mixed feeding, and oral Rothia on early childhood caries
(2024-06-24) Szeto, Andrea; Chelikani, Prashen (Oral Biology); Klus, Bradley (Preventive Dental Science); Menon, Anil (Preventive Dental Science); Schroth, Robert
Objective: To investigate the association between feeding practices (exclusive breastfeeding, exclusive bottle-feeding, and mixed) with early childhood caries (ECC) and the association between the prevalence of oral Rothia, at the species and genus level, with ECC. Methods: A total of 438 children (178 caries-free, 260 with ECC) were included in this case-control study. A comprehensive questionnaire that included a section on feeding history, was completed by the parent or caregiver of each participant. Based on the feeding history responses, participants were classified as either exclusively breastfed, exclusively bottle-fed, or mixed (both bottle-fed and breastfed). A supragingival plaque sample was collected from each participant and then assessed with 16S rRNA sequencing for Rothia genus and species’ relative abundances. The association between feeding practices and Rothia prevalence with ECC, accounting for confounding variables, was analyzed using multivariable logistic regressions. Results: A low relative abundance of Rothia aeria was significantly associated with ECC (p<0.05), whereas there were no significant associations found between the relative abundance of Rothia dentocariosa or Rothia mucilaginosa with caries status (p>0.05). While the odds of association between a low relative abundance of Rothia (genus) and ECC was 1.63, this relationship failed to reach the threshold of significance (p=0.054). Feeding practices were not significantly associated with ECC after adjusting for confounding variables. However, bedtime bottle use, bedtime snacking, living in a rural/remote area, being an older age, the use of fluoridated toothpaste, and having less-educated guardians were significantly associated with ECC (p<0.05) Conclusions: Findings in this study suggest that low relative abundances of R. aeria and Rothia (genus) are associated with ECC. Feeding practices were not key risk factors for ECC in this sample, as other factors related to the social environment and bedtime habits were more strongly associated. Since the current literature is limited, prospective studies examining Rothia and feeding practices with ECC would be beneficial to understand the causal relationship between Rothia and ECC and to help reach a consensus on the effect of different feeding practices on ECC risk.
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Open Access
Establishing cephalometric norms for the Indian population using Steiner's cephalometric analysis
(2024-06-20) Manohar, Mithun King; Rykiss, Jared (Preventive Dental Science); Mutalik, Vimi S (Preventive Dental Science); Anand, Dharani (Sri Ramachandra Dental College); Wiltshire, William
Objective: Current cephalometric norms are based on an untreated Caucasian sample and may not apply to other ethnic groups. It is essential to establish standard norms for different populations. Aim: To create cephalometric norms for the Indian population by utilizing Steiner’s analysis to aid in diagnosis and treatment planning. Method: The sample consisted of 200 adult subjects of Indian ethnic origin (100 males and 100 females). To avoid regional bias, samples were collected from four metropolitan cities: Delhi, Mumbai, Calcutta, and Chennai. The primary inclusion criterion required the participants to have a Class I molar relationship and an aesthetically pleasing profile (assessed through intra-oral and extra-oral profile photographs). All the radiographs were traced digitally using Dolphin (version 11.95) in random order by a single operator to reduce bias. Another operator randomly selected and retraced fifty cephalograms to check the operator's reliability and reproducibility. Inter-operator and intra-operator reliability was deemed satisfactory. Steiner’s cephalometric analysis was used to compare each participant's cephalogram, calculating all variables' means and standard deviations. Unpaired t-tests were used to determine differences in variable means between the Indian and Caucasian populations. The probability value (P value) of 0.05 was considered statistically significant. Results: Significant variations in specific parameters of Steiner’s cephalometric analysis were found between Indian and Caucasian populations. Steiner’s analysis showed a significant increase (P<0.05) in SNA (84°), SNB (82°), SND (79°), U1 to NA (8mm), U1 to NA (28°), L1 to NB (7mm), L1 to NB (28°), and reduced Go-Gn to SN (26°), Interincisal angle (122°), Occ plane to SN (12°) while ANB remained constant. Conclusions: This study emphasizes the necessity of establishing cephalometric norms for the Indian population. Understanding cephalometric differences in norms for various ethnic groups is critical for customized diagnosis and treatment.
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Open Access
The non-inflammatory role of macrophage migration inhibitory factor in regulating insulin resistance and hypertriglyceridemia
(2024-07-08) Huang, Yiheng; Shen, Garry (Internal Medicine); Marzban, Lucy (Pharmacy); Zhang, Dawei (University of Alberta); Qi, Dake
Insulin resistance (IR) and hypertriglyceridemia are two major symptoms of metabolic dysfunction, which are regulated by endocrine function and lipid storage in white adipose tissue (WAT). Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine regulating metabolic dysfunction. We currently identified how adipose MIF regulated IR and hypertriglyceridemia through the following mechanisms. (1) MIF is involved in the development of non-inflammatory IR by a cross-talk between preadipocyte factor 1+ (Pref-1+) cells and adipocytes in WAT. Pref-1 expression is negatively associated with circulating MIF levels in obese human subjects and animal models in the absence of adipose inflammation. Pref-1 is released from Pref-1+ cells including M2 (anti-inflammatory) macrophages, endothelial cells or progenitors in WAT. Its release inhibits MIF derived from both Pref-1+ cells and adipocytes by binding with integrin β1 and inhibiting the mobilization of p115. High palmitic acid (PA) induces protease-activated receptor 2 (PAR2) expression in Pref-1+ cells, thereby downregulating Pref-1 expression and release in an AMP-activated protein kinase (AMPK)-dependent manner. The loss of Pref-1 increases adipose MIF secretion contributing to non-inflammatory IR in obesity. In contrast, treatment with Pref-1 blunts the increase in circulating plasma MIF levels and subsequent IR induced by a high palmitic acid diet (PD). (2) MIF inhibits lipoprotein lipase (LPL) that catalyzes the degradation of plasma triglyceride (TG) and upregulates adipose lipid storage. LPL hydrolyzes circulating TG to release free fatty acids (FFAs) and it promotes lipid storage in WAT. Obesity-associated high PAR2 expression is inversely correlated with LPL expression in WAT, leading to hypertriglyceridemia. MIF reduces LPL expression and activity in adipocytes. High circulating MIF levels in mice models with PD feeding or high MIF expression suppress adipose LPL, which is associated with increased plasma TG levels. However, the low adipose LPL expression and activity is reversed in Par2-/- mice. Thus, high PA increased activation of PAR2, facilitating adipose MIF secretion, and then resulted in low LPL-induced hypertriglyceridemia. We identified the mechanisms of MIF in mediating IR and hypertriglyceridemia in both human subjects and animal models. Our translational research will provide important clinical implications for the development of new therapeutic strategies for metabolic syndrome.
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Open Access
Utilization of silver diamine fluoride by dentists in Canada: a review of the non-insured health benefits dental claims database.
(2024-06-24) El Azrak, Mohamed; Bertone, Mary (School of Dental Hygiene); Klus, Bradley (Preventive Dental Science); Menon, Anil (Preventive Dental Science); Schroth, Robert
Introduction: Dental caries is one of the most frequent chronic conditions in childhood. Silver diamine fluoride (SDF) is a recognized caries arresting agent, but its use is relatively new in Canada. SDF has the potential to arrest early childhood caries in young children and delay treatment until children can be seen in outpatient settings. In August 2020 the Non-Insured Health Benefits (NIHB) program of the Department of Indigenous Services Canada approved the following procedure “Topical application to hard tissue lesion(s) of an antimicrobial or remineralization agent (includes silver diamine fluoride)”. The purpose of this study was to investigate the utilization of SDF by Canadian dental providers for First Nations and Inuit Canadians with dental benefits through the NIHB program. Methods: The NIHB program provided data on all claims paid for the procedure “topical antimicrobials or remineralization agent/SDF” for children < 17 years and any other procedure claimed on the same date for the period from August 1, 2020 to July 31, 2022 in all Canadian provinces and territories with the exception of British Columbia, Newfoundland and Labrador, and Prince Edward Island. Claims made by general dentists, pediatric dentists, prosthodontists, and dental hygienists were included. The claims from August 2020 until July 2022 were arranged into eight,3 months, quarters. Rates of SDF application by province or territory were calculated. Data were analyzed using NCSS 2023 Statistical Software. Statistical analyses included descriptive statistics (frequencies, mean ± standard deviations (SD)). Results: There were 4,158 claims for SDF between August 1, 2020 and July 31, 2022 for 3,465 children <17 years of age. The mean age was 7.9 ± 4.0 years and 52.9% of those were female. The majority of claims, both for the initial claim (87.1%) and follow up visit claims, were made by general dentists. Most children had another procedure at the initial and follow up visits, with claims being for one or more assessment, non-restorative, restorative, or sedation procedures. Claims revealed that traditional restorative treatment was also performed on the same day of SDF application for nearly one third of patients. The province with the most initial claims for SDF was Manitoba (19.6%). However, Alberta was the highest province for follow-up claims for SDF. Nunavut and Northwest Territories had the highest rates of SDF claims for children (37.0/1,000) and (20.9/1,000) respectively. Quarter 8 had the highest number of initial claims (539) for SDF submitted. Claims appear to be lower during the period of November to January compared to the rest of the year. Conclusions: Data suggest that there has been an overall continuous increase in the number of claims submitted for SDF among registered First Nations and Inuit children. Claims for SDF have been submitted by providers in the majority of Canadian provinces and territories from August 2020 until July 2022. Although, Ontario and the Western provinces had the highest number of claims, Nunavut and the Northwest Territories had the highest rates of claims.
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Open Access
Simulation and experimentation of a MEMS electrostatic field sensor with a floating ground
(2024-07-01) Kaskiw, Joel; Filizadeh, Shaahin (Electrical and Computer Engineering); Kordi, Behzad (Electrical and Computer Engineering); Shafai, Cyrus
This thesis presents the simulation and experiments performed on a Micro-Electro-Mechanical System (MEMS) electrostatic field sensor with a virtual ground. Because of their small form factor and low power consumption, MEMS electrostatic field sensors offer a promising alternative to commonly used devices such as field mills. Four separate simulations were conducted on the device, each with varying parameters to gain an understanding of how the device behaves when exposed to a 10kV DC voltage carrying wire. The simulation environment was designed to mimic the experimental conditions as close as possible. That being, simulation #1 tested the device moving towards the high voltage wire from the ground plane, the second simulation preformed had the device moving away from the wire while in contact with the ground plane. The third and fourth simulations added a wooden pole to act as a handle, this was done to mimic a possible real-world application. In these two simulations the device was tested at different heights from the ground plane and at different distances from the high voltage carrying wire. The results of these simulations were then compared to analytically obtained values, of which the simulated values agreed. Five experiments were conducted in the University of Manitoba’s High Voltage Laboratory of which four were completed with the same environment as the simulations to ensure the results have as little discrepancy as possible. Experiment #1 was setup the same as simulation #1 and so on. The fifth experiment was conducted to see the behavior of the device in a potential real-world environment where a surface has become energized. A close correlation between the simulated, calculated, and experimental values were achieved. In addition, control electronics and a Printed Circuit Board (PCB) were developed for the sensor that allowed it to be used in the experiments to collect data and have it perform as it would in real world setting. This system included a wireless data transmission system over a 2.4 GHz radio that allows the user to be physically separated from the device when taking readings, reducing the danger from high voltage sources, a display that allows the user to visually see the output from the device and finally, the ability for the output of the sensor to be recorded, this recorded data could then be used to help determine the behaviour of the sensor. After all simulations and experiments we completed, it was determined that the sensor has a response that follows the predicted behavior by the four simulations and the analytical values.
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Open Access
Optimization of geometric measures of sets of moving objects
(2024-06-20) Penha Costa, Ikaro Ruan; Li, Ben (Computer Science); Kirkland, Steve (Mathematics); Bose, Prosenjit (Carleton University); Durocher, Stephane
Given a set S of objects, each moving with linear motion in R^d, consider the diameter D(S, t) of S at time t. In this thesis we explore optimization of extent and proximity measures of S. For instance, one possibility is to identify minimum diameter D(S, t) of S over the domain of time t. D(S, t) is an example of a measure of extent of S. On the basis of this model, other geometric measures could also be explored to be optimized for sets of objects in motion. Let n be the cardinality of S and let M(S, t) be a geometric measure of extent or proximity at time t. Given an integer k, select a subset Q ⊂ S such that |Q| = k and Q has extreme measure M(Q, t) over all possible subsets Q of cardinality k. The present thesis focuses on minimizing and maximizing M(Q, t), in one and two dimensions (d = 1 or d = 2), for which the measure corresponds to set diameter, set width, minimum axis-aligned bounding box, and minimum enclosing disk. For each measure, exact polynomial-time algorithms are proposed for selecting an optimal subset of S and finding the time t of which the subset optimizes the measure.
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Embargo
Assessing in vitro methodologies for the determination of protein digestibility, amino acid digestibility, and protein quality
(2024-06-24) Bui, Nguyen; Aluko, Rotimi (Food and Human Nutritional Sciences); Nyachoti, Martin (Animal Science); James, House
This study examined the potential of two in vitro static digestion models, namely the pH-drop and INFOGEST 2.0, to determine in vitro protein digestibility and amino acid digestibility in assessing protein quality. The pH-drop model directly measured in vitro protein digestibility for the subsequent calculation of the in vitro Protein Digestibility Corrected Amino Acid Score (IV-PDCAAS) value. However, the INFOGEST model digestion products were analyzed by three methods: i) OPA derivatization, ii) total nitrogen via Kjeldahl, and iii) individual amino acid analysis to determine in vitro protein digestibility and IV-PDCAAS. The latter analysis was additionally used to assess in vitro amino acid digestibility, subsequently used to calculate in vitro Digestible Indispensable Amino Acid Score (IV-DIAAS). Among the four assessment methods, the OPA assay and total amino acid analysis from the INFOGEST digestion products demonstrated closer associations with in vivo PDCAAS compared to the pH-drop model and the Kjeldahl analysis. However, the pH-drop model, with a straightforward and simple approach, exhibited better repeatability across measurements. Using three popular assays, the PDCAAS, the DIAAS, and the Protein Efficiency Ratio (PER), to evaluate protein quality and permitted protein content claims of samples, it was observed that there was no difference in terms of protein content claims determined when using the in vivo or four in vitro methodologies. The results indicated that the PDCAAS generally offered higher protein permitted claims than the DIAAS and the PER methods and their respective protein content claims, highlighting that the selection of assessment methods impacts the limiting amino acid and protein quality and extends to subsequent claims for the sample. In conclusion, the pH-drop model is straightforward and highly repeatable; however, the INFOGEST model showed a closer correlation with in vivo data. Additionally, the in vitro static INFOGEST digesta proved versatile in evaluating various aspects of protein quality in both in vitro protein and amino acid digestibility through amino acid analysis. Both models can be valuable screening tools for protein quality assessment. Further development of these in vitro methodologies can offer effective and sustainable non-animal testing alternatives for protein quality assessment and protein content claims on product packaging.