Towards a model for evaluating student learning via e-assessment

The need for practical tools to assess student learning at the course level is becoming a more pressing goal for all academic institutions. This is because learning assessment tools which monitor both student performance and conceptual change events that lead to improved learning ultimately provide the basis for the subsequent assessments of programs and institutions. In performing effectively in this capacity, a viable and efficient assessment tool at the course level possesses the following characteristics; 1) the ability to be integrated effectively within the existing course structure, 2) the ability to generate quantitative, measurable results, and 3) the ability to provide timely feedback. This paper proposes a model for assessing student learning at the course level which utilizes, in part, online assessment methods (eAssessments) to achieve these characteristics. More specifically, the model provides a description of how assessment may be embedded into an existing course and illustrates the utilization of online pre/post-tests and knowledge surveys as a source of assessment data. The data analysis, based in part upon Bloom's revised taxonomy, is then discussed together with how the results are used to determine the level of learning achieved. The paper concludes with a proposal for an experiment wherein the model is tested to determine its ability to detect changes in student learning originating from the implementation of a pedagogical strategy such as online tutoring

Ion Beam Sputtered Coatings of Bioglass

The ion beam sputtering technique available at the NASA-Lewis was used to apply coatings of bioglass to ceramic, metallic, and polymeric substrates. Experiments in vivo and in vitro described investigate these coatings. Some degree of substrate masking was obtained in all samples although stability and reactivity equivalent to bulk bioglass was not observed in all coated samples. Some degree of stability was seen in all coated samples that were reacted in vitro. Both metallic and ceramic substrates coated in this manner failed to show significantly improved coatings over those obtained with existing techniques. Implantation of the coated ceramic substrate samples in bone gave no definite bonding as seen with bulk glass; however, partial and patchy bonding was seen. Polymeric substrates in these studies showed promise of success. The coatings applied were sufficient to mask the underlying reactive test surface and tissue adhesion of collagen to bioglass was seen. Hydrophilic, hydrophobic, charged, and uncharged polymeric surfaces were successfully coated

Understanding ageing - the role of mitochondria in determination of caenorhabditis elegans life span

Mitochondria are organelles found in eukaryotic cells. They are involved in many vital cellular functions. Consequently, mitochondrial dysfunction leads to a variety of human disorders. Many studies of the last 50 years showed that mitochondria are involved in the regulation of physiological ageing. However, the underlying mechanisms are still unknown. We aimed to analyze the mitochondrial role in ageing in Caenorhabditis elegans model system. Its short life cycle, powerful genetic tools and known fates of all 959 post-mitotic somatic cells make this nematode an excellent model system for ageing studies. Besides numerous advantages, the small body size of the worm brings along certain technical limitations. We developed a toolkit to analyze mitochondrial morphology, metabolic profile and electron transport chain (ETC) activities on a single-tissue level. In addition, we adapted a method for analysis of mtDNA copy number for use on individual animals. Each mitochondrion has its own genome that is maintained by mitochondrial DNA polymerase gamma (POLG). By analyzing polg-1 mutant worms that are deficient in the sole mitochondrial DNA polymerase, we showed that C. elegans mtDNA replication mainly takes place in the gonad, the only proliferative tissue in adult worms. Thus mtDNA depletion leads to marked dysfunction of this organ. Severe mtDNA depletion leads to embryonic arrest, whereas mild depletion does not affect development. We showed that mtDNA replication does not take place during embryogenesis; it starts during the L3 larval stage, correlating with germline proliferation. Taken together, mtDNA copies in the somatic tissues mainly stem from the oocyte and stay relatively unchanged during development and early adulthood. Remarkably, somatic tissues are not severely affected in polg-1 deficient animals despite the marked overall mtDNA depletion in contrast to other model systems, namely flies and mice. Furthermore, we showed that mtDNA copy number exhibits substantial plasticity upon environmental stress. Mitochondria are the major source of ATP, which they form by oxidative phosphorylation (OXPHOS). Defective OXPHOS often results in severe phenotypes or premature death in several animal models. However, studies in C. elegans showed that dysfunction in the mitochondrial respiratory chain is not necessarily lethal. It can rather result in lifespan prolongation in the so-called “Mit mitochondrial) mutants”. We analyzed molecular mechanisms that underlie the longevity induced by mitochondrial dysfunction. It has been shown that different mechanisms can affect the longevity of Mit mutants. We found that succinate dehydrogenase activity of electron transport chain (ETC) complex II (CII) influences the lifespan of Mit mutants independently of the insulin-like/IGF-1 pathway. We showed that mitochondrial unfolding protein response (UPRmt) is up-regulated in both short- and long-lived Mit mutants. Furthermore, our results suggest that respiration rate is not necessarily linked to longevity. Analysis of several metabolic pathways in Mit mutants revealed that dysfunction of the mitochondrial respiratory chain leads to a common response characterized by up-regulation of the citric acid cycle, glycolysis, and some anaerobic pathways, accompanied by increase in neutral fat storage

Synthesis and characterization of novel scaffold for bone tissue engineering based on Whartons´s jelly

A composite is a material made of more than one component, and the bond between the components is on a scale larger than the atomic scale. The objective of the present study was to synthesize and perform the structural characterization and biological evaluation of a new biocomposite (BCO) based on a novel combination of an organic and an inorganic phase, for bone tissue engineering applications. The organic phase consisted of Wharton´s Jelly (WJ), which was obtained from embryonic tissue following a protocol developed by our laboratory. The inorganic phase consisted of bioceramic particles (BC), produced by sintering hydroxyapatite (HA) with β- tricalcium phosphate (β-TCP), and bioactive glass particles (BG). Each phase of the BCO was fully characterized by SEM, EDS, XRD and FTIR. Biocompatibility was evaluated in vivo in the tibiae of Wistar rats (n=40). Histological evaluation was performed at 0, 1, 7, 14, 30 and 60 days. XRD showed the phases corresponding to HA and β-TCP, whereas diffractogram of BG showed it to have an amorphous structure. EDS showed mainly Si and Na, Ca, P in BG, and Ca and P in HA and β-TCP. FTIR identified bonds between the organic and inorganic phases. From a mechanical viewpoint, the composite showed high flexural strength of 40.3±0.8MPa. The synthesized BCO exhibited adequate biocompatibility as shown by formation of lamellar type bone linked by BG and BC particles. The biomaterial presented here showed excellent mechanical and biocompatibility properties for its potential clinical use.Fil: Martinez, Cristian. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; Argentina. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Anatomía Patológica; Argentina. Universidad Nacional de Cuyo. Facultad de Odontologia; ArgentinaFil: Fernández, Carlos. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; ArgentinaFil: Prado, Miguel Oscar. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ozols, Andres. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; ArgentinaFil: Olmedo, Daniel Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Odontología. Cátedra de Anatomía Patológica; Argentin

Preparation and in vitro characterization of novel bioactive glass ceramic nanoparticles

SiO2-CaO-P2O5 ternary bioactive glass ceramic (BGC) nanoparticles with different compositions were prepared via a three-step sol-gel method. Polyethylene glycol was selected to be used as the surfactant to improve the dispersion of the nanoparticles. The morphology and composition of these BGC nanoparticles were observed by ESEM and EDX. All the BGC particles obtained in this method were about 20 nm in diameter. XRD analysis demonstrated that the different compositions can result in very different crystallinities for the BGC nanoparticles. Bioactivity tests in simulated body fluid solution (SBF), and degradability in phosphate buffer solution (PBS), were performed in vitro. SEM, EDX, and XRD were employed to monitor the surface variation of neat poly(L-lactic acid), PLLA, foam and PLLA/BGC porous scaffolds during incubation. The BGC nanoparticles with lower phosphorous and relative higher silicon content exhibited enhanced mineralization capability in SBF and a higher solubility in PBS medium. Such novel nanoparticles may have potential to be used in different biomedical applications, including tissue engineering or the orthopedic field.Contract grant sponsor: FCT; contract grant numbers: POCTI/FIS/61621/2004, SFRH/BPD/25828/2005, PTDC/QUI/69263/200

In situ study of partially crystallized bioglass (R) and hydroxylapatite in vitro bioactivity using atomic force microscopy

The present work investigates, in situ, the in vitro bioactivity of partially crystallized 45S5 Bioglass! (BG) as a function of immersion time in a simulated body fluid (SBF) using atomic force microscopy (AFM). The results obtained for the crystallized BG! were compared to those of hydroxyapatite c- and a-faces. The calcium phosphate layer grows on the crystallized 45S5 B! by multiple two-dimensional nucleation and fusion of these two-dimensional islands, which is essentially the same mode as for the hydroxyapatite c-face. The surface of the crystallized 45S5 BG! was almost fully covered with a dense and compact calcium phosphate layer after 24 h. The calcium phosphate formation on the crystallized BG! arises from a low surface energy of the surface layer and/or an effect of the layer to lower the resistance when the growth units of calcium phosphate incorporate into the growing island. These results indicate that the crystallized 45S5 BG! is suitable to be used as a filler for polymeric matrix bioactive composites, as it maintains a high bioactivity associated with a stiffer behavior (as compared to standard BG!)