TESTING THE THEORY OF THRESHOLD CONCEPTS IN A CONTEXT OF DENTAL EDUCATION. PRELIMINARY ANALYSIS.

This paper reports on the pilot phase of a phenomenographic study which explores the relationship between teachers’ and students’ perceptions of the curriculum and theory of threshold concepts, which claims that there are concepts in all disciplines which must be understood, if learners are to progress to a more advanced level of understanding. It is suggested that threshold concepts may represent ways of thinking and practising within disciplines [1]. In this study consideration is given to the troublesome aspects of knowledge as described by David Perkins (1999) [2] and further developed by Meyer and Land (2003) [3]. Researcher’s intention is to investigate if students experience any conceptual difficulties and what the nature of these might be. Students’ and teachers’ accounts of how they perceive the dental curriculum might help to verify if there is a relationship between the curriculum and the theory of threshold concepts. Analysis of the troublesome aspects of knowledge may lead to the identification of threshold concepts in the dental curriculum

Properties of TiO2 coatings applied by atomic layer deposition (ALD) on 100Cr6 steel

The paper presents the method of forming TiO2 coatings on 100Cr6 steel using the ALD method and assessing the properties of the obtained coatings. The coatings were assessed in terms of surface morphology, chemical composition, contact angle and tribological properties. The performed tribological tests show that TiO2 coatings are characterized by lower resistance to motion. During measuring the geometric structure of surfaces on samples with TiO2 coating, smaller wear traces were recorded than for 100Cr6 steel. The obtained values of the contact angles prove that the 100Cr6 steel coated with TiO2 is more hydrophobic than the uncoated 100Cr6 steel. TiO2 coatings can be used in low-loaded tribological systems and as barrier coatings

Properties of TiO2 coatings applied by atomic layer deposition (ALD) on 100Cr6 steel

The paper presents the method of forming TiO2 coatings on 100Cr6 steel using the ALD method and assessing the properties of the obtained coatings. The coatings were assessed in terms of surface morphology, chemical composition, contact angle and tribological properties. The performed tribological tests show that TiO2 coatings are characterized by lower resistance to motion. During measuring the geometric structure of surfaces on samples with TiO2 coating, smaller wear traces were recorded than for 100Cr6 steel. The obtained values of the contact angles prove that the 100Cr6 steel coated with TiO2 is more hydrophobic than the uncoated 100Cr6 steel. TiO2 coatings can be used in low-loaded tribological systems and as barrier coatings

Influence of surface roughness on selected properties of the TiAlN coating

The HS6-5-2C steel samples with different surface roughness were used for the tests. After grinding had a roughness parameter of Ra = 0,03 μm, and after polishing Ra = 0,01 μm. A TiAlN coating was applied to the substrate prepared in this way. Using a confocal microscope with an interferometric mode, the geometrical structure of the samples was analyzed. The optical strain gauge was used to measure the contact angle. Tribological tests were carried out in conditions of technically dry friction. The polished sample with the coating was characterized by a more stable course of the friction coefficient, lower wear and a smaller wetting angle

The impact of adult mortality on household dissolution and migration in rural South Africa.

OBJECTIVE: To investigate the effect of adult death on household dissolution and migration. DESIGN: Demographic surveillance of the population in a rural area of northern KwaZulu Natal, South Africa. METHODS: Data on households resident in the surveillance area on 1 January 2000 were used to examine the effect of adult mortality and household risk factors on household dissolution and mobility between January 2000 and October 2002. Cox regression models were used to assess the risk of household dissolution and migration, controlling for multiple risk factors including causes of death, household composition and household assets. RESULTS: By October 2002, 238 households (2%) had dissolved and 874 (8%) migrated out of the area; 21% (2179) of all households had at least one adult death (18 years and older). Households where one or more adult members died during the follow-up period were four times more likely to dissolve, after controlling for household and community level risk factors [4.3; 95% confidence interval, (CI), 3.3-5.7]. The risk of dissolution was significantly higher in households with multiple deaths (2.3; 95% CI, 1.3-4.3). There were no significant differential risks associated with cause of death, age or sex of the deceased. Adult mortality in the household was not associated with migration. CONCLUSIONS: Poorer households, as measured by asset ownership, and households trying to cope with adult deaths are vulnerable to dissolution. The dramatic increase in adult mortality attributable to AIDS will increase the number of households that do not survive as a functional and cohesive social group

The influence of environmental conditions on the tribological properties of the Ti13Nb13Zr alloy

The paper presents the results of tribological tests of the Ti13Nb13Zr titanium alloy - carried out in the conditions of lubrication with liquids simulating body fluids. Artificial saliva solutions were used for the tests. Two pH values were used – 7,0 characteristic of a healthy organism and 4,9 - typical for the presence of inflammation. The countersample in the tested friction nodes were Al2O3 balls with a diameter of 6 mm loaded with a normal force of 1 N. The tests obtained showed a strong influence of environmental conditions on the tribological properties of the Ti13Nb13Zr titanium alloy. This applies to both the value of the coefficient of friction and linear wear. In the case of tests carried out under lubrication conditions with an artificial saliva solution at pH 7,0 they were 0,47 and 31,1 μm, respectively; in the case of a fluid at pH 4,9 they were 25 % and 45 % higher (0,62 and 65,6 μm)

The influence of environmental conditions on the tribological properties of the Ti13Nb13Zr alloy

The paper presents the results of tribological tests of the Ti13Nb13Zr titanium alloy - carried out in the conditions of lubrication with liquids simulating body fluids. Artificial saliva solutions were used for the tests. Two pH values were used – 7,0 characteristic of a healthy organism and 4,9 - typical for the presence of inflammation. The countersample in the tested friction nodes were Al2O3 balls with a diameter of 6 mm loaded with a normal force of 1 N. The tests obtained showed a strong influence of environmental conditions on the tribological properties of the Ti13Nb13Zr titanium alloy. This applies to both the value of the coefficient of friction and linear wear. In the case of tests carried out under lubrication conditions with an artificial saliva solution at pH 7,0 they were 0,47 and 31,1 μm, respectively; in the case of a fluid at pH 4,9 they were 25 % and 45 % higher (0,62 and 65,6 μm)

Influence of surface roughness on selected properties of the TiAlN coating

The HS6-5-2C steel samples with different surface roughness were used for the tests. After grinding had a roughness parameter of Ra = 0,03 μm, and after polishing Ra = 0,01 μm. A TiAlN coating was applied to the substrate prepared in this way. Using a confocal microscope with an interferometric mode, the geometrical structure of the samples was analyzed. The optical strain gauge was used to measure the contact angle. Tribological tests were carried out in conditions of technically dry friction. The polished sample with the coating was characterized by a more stable course of the friction coefficient, lower wear and a smaller wetting angle

Primary merkel cell carcinoma clinically presenting as deep oedematous mass of the groin

Merkel cell carcinoma (MCC) is a relatively rare, polyomavirus associated, primary neuroendocrine carcinoma of the skin which is usually arising from dermal skin layers. However, the origin of MCC in the subcutaneous tissue is debatable. We report a 58-yearold female patient with an oedematous mass on her left groin that was firm in consistency and had no discoloration or other visible abnormality of the overlying skin. On histology and immunohistology the tumour was consistent with the diagnosis of MCC showing a predominant subcutanous growth pattern. Pelvic magnetic resonance tomography revealed a tumour conglomerate reaching from the subcutis of the left groin to the left paraaortal and parailiacal region indicating widespread lymphogenic metastisation. Despite complete medical work-up no other MCC primary could be detected. In conclusion, predominant subcutaneous growth pattern as well as tumour localization in the groin are uncommon features of MCC. MCC showing the aforementioned features may be associated with significant delay of diagnosis and therefore represents an unfavourable prognostic factor