![]() ![]() It is responsible for delayed tanning and burning in addition to these short-term effects it enhances skin ageing and significantly promotes the development of skin cancer. Medium-wavelength UVB is very biologically active but cannot penetrate beyond the superficial skin layers. ![]() However, it is completely filtered by the atmosphere and does not reach the earth's surface. Short-wavelength UVC is the most damaging type of UV radiation. The UV region covers the wavelength range 100-400 nm and is divided into three bands: However, shorter wavelength UV radiation is less able to penetrate the skin. The shorter the wavelength, the more harmful the UV radiation. They differ in their biological activity and the extent to which they can penetrate the skin. The three types of UV radiation are classified according to their wavelength. Raised awareness and changes in life-style are urgently needed to alter ongoing trends. More outdoor activities and altered sunbathing habits often result in excessive UV exposure. However, most evidence now suggests that the major cause for the increased cancer rates is altered behaviour rather than ozone depletion. Some people claim that this is due to ozone depletion and enhanced levels of UV. The incidence of different types of skin cancer has been growing dramatically over the past decades. A full recovery of the ozone level is not expected until 2050. However, the long life span of the chemicals already released will cause ozone depletion problems to persist for many years to come. International agreements, in particular the Montreal Protocol, are gradually succeeding in phasing out the production of ozone-depleting substances. Ozone depletion is caused by human-made chemicals released into the atmosphere and will continue until the use of chlorine and bromine compounds is drastically reduced. Consequently, the people and the environment are exposed to higher levels of UV radiation, especially UVB. As the ozone layer gets thinner, the protective filter activity of the atmosphere is progressively reduced. ![]() It is further expected that the findings of this study may contribute to effective re-design of MOOC platform forums, more effective and efficient TA interventions and ultimately to improved learning.Ozone is a particularly effective absorber of UV radiation. Such issues cause various problems to teaching assistants, hindering effective support to learners and therefore affecting the learners’ experience. The results of this study indicate that the OpenEdX forum design faces a variety of issues that need to be considered by course designers. Moreover, through interviews with the TAs, problems they faced while supporting learners were confirmed. The goal was to reveal any design issues initially through a participatory ethnographic study and complementarily through a formal usability evaluation. Towards this objective, a mixed-methods study was performed on two MOOCs delivered through the OpenEdX platform. In this paper, we investigate the impact a forum design can have on the TA’s effectiveness while supporting the learners of a MOOC. Teaching Assistants (TAs) have a crucial role coordinating and supporting learners within a MOOC forum. This communication has been shown that can have strong learning impact. Structured communication between learners or between learners and instructors can take place through the forum. The discussion forum is a key part of a MOOC platform. Massive Open Online Courses (MOOCs) are delivered through dedicated platforms that provide educational opportunities to a large number of learners around the globe. ![]()
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