Nicotinic Receptor Alpha7 Expression during Tooth Morphogenesis Reveals Functional Pleiotropy

The expression of nicotinic acetylcholine receptor (nAChR) subtype, alpha7, was investigated in the developing teeth of mice that were modified through homologous recombination to express a bi-cistronic IRES-driven tau-enhanced green fluorescent protein (GFP); alpha7GFP) or IRES-Cre (alpha7Cre). The expression of alpha7GFP was detected first in cells of the condensing mesenchyme at embryonic (E) day E13.5 where it intensifies through E14.5. This expression ends abruptly at E15.5, but was again observed in ameloblasts of incisors at E16.5 or molar ameloblasts by E17.5–E18.5. This expression remains detectable until molar enamel deposition is completed or throughout life as in the constantly erupting mouse incisors. The expression of alpha7GFP also identifies all stages of innervation of the tooth organ. Ablation of the alpha7-cell lineage using a conditional alpha7Cre×ROSA26-LoxP(diphtheria toxin A) strategy substantially reduced the mesenchyme and this corresponded with excessive epithelium overgrowth consistent with an instructive role by these cells during ectoderm patterning. However, alpha7knock-out (KO) mice exhibited normal tooth size and shape indicating that under normal conditions alpha7 expression is dispensable to this process. The function of ameloblasts in alpha7KO mice is altered relative to controls. High resolution micro-computed tomography analysis of adult mandibular incisors revealed enamel volume of the alpha7KO was significantly reduced and the organization of enamel rods was altered relative to controls. These results demonstrate distinct and varied spatiotemporal expression of alpha7 during tooth development, and they suggest that dysfunction of this receptor would have diverse impacts upon the adult organ

Learning Competencies, Experiences and Problems Encountered in the Implementation of Graduate Programs of Visayas State University during the COVID-19 Pandemic

The Covid-19 pandemic caused an unprecedented ongoing global problem which affect different people in different ways. The study was conducted to know the effects of this world wide pandemic to graduate students in VSU and to look into the problems they encountered as well as the various coping mechanisms especially in dealing with the virtual delivery of instructions. This will provide vital information for institutional planning in the implementation of graduate programs in the university during the Covid-19 pandemic. This study was conducted through online survey involving 200 graduate students as part of the graduate tracer studies of the university. Majority of the problems identified include the following: no stable internet connectivity; inaccessibility of laboratory facilities because of restrictions to enter the university campus; difficulty in conducting thesis analysis; unable to meet the deadlines in submitting required printed copy of reports because of long delayed shipment; inaccessibility of books in the library necessary for the preparation and discussion of thesis; laboratory exercises were difficult to accomplished due to inaccessibility to laboratory equipment and facilities and difficulty in understanding some complex lessons with virtual study delivery. In addition, they also emphasized that online mode of learning is more stressful that causes anxiety and mental illness. The online discussions were quite difficult and laboratory principles could not be well understood because of no actual practical laboratory activities in technical courses; so many distractions and noises in students' surroundings with the virtual mode of teaching delivery; hard time searching for resources and lots of requirements and activities to comply. The respondent likewise gave some suggestions to improve the online delivery of instructions. These include the provision of recorded class discussions, longer hours in taking online exams, transparency of grading system and healthy environment between the teacher and students.</jats:p

Prediction of wave resistance by a Reynolds-averaged Navier–Stokes equation–based computational fluid dynamics approach

The prediction of wave resistance in naval architecture is an important aspect especially at high Froude numbers where a great percentage of total resistance of ships and submerged bodies is caused by waves. In addition, during hull form optimization, wave resistance characteristics of a ship must closely be observed. There are potential, viscous and experimental methods to determine the wave resistance of a ship. Reynolds-averaged Navier-Stokes equation-based methods usually follow the experimental method that determines the form factor first. However, it is proven in recent studies that the form factor changes with the Reynolds number. As the Reynolds number increases, this change in the form factor is being neglected. In this study, a Reynolds-averaged Navier-Stokes equation-based prediction of wave resistance is presented that overcomes this flaw. The methodology is validated with the benchmark problems of submerged and surface-piercing bodies to determine the effectiveness of the proposed method. The method is also validated by experiments carried out at the Ata Nutku Ship Model Testing Laboratory of Istanbul Technical University for a totally submerged ellipsoid and the benchmark KRISO Containership. Results reveal the robustness of the present methodology