Articular cartilage is a mechanically important soft tissue whose organisation at the micro- and nanoscale is critical for healthy joint function and where degeneration is associated with widespread disorders such as osteoarthritis. The tissue possesses a complex, graded and depth-dependent structure and at the nanoscale, cartilage mechanical functionality is dependent on the collagen and hydrated proteoglycans that form the extracellular matrix. The structure and in situ dynamic response of the collagen fibrils at the nanoscale, however, remain unclear. Here we utilise small angle X-ray diffraction to measure the depth-wise structure of the fibrillar architecture whilst performing time-resolved measurements during compression of bovine and human cartilage explants. We demonstrate the existence of a depth-dependent fibrillar pre-strain as determined by the D-periodicity, estimated at approximately 1-2%, due to osmotic swelling pressure from the proteoglycans. Furthermore, we reveal a rapid reduction and recovery of this pre-strain during stress relaxation, approximately 60 seconds after onset of peak load. Selective proteoglycan removal disrupts both collagen fibril pre-strain and transient responses during stress relaxation. Additionally, we show that IL-1β induced tissue inflammation also results in a reduction in fibrillar pre-strain and altered fibrillar mechanics. Cyclic loading induces a dynamic reduction and recovery in the D-period that is present regardless of loading rate or treatment, along with changes in diffraction peak intensities and widths. These findings suggest that the fibrils respond to loading via intra- and inter-fibrillar disordering alongside a transient response that is mediated by changes in hydration. These are the first studies to highlight previously unknown transient and cyclic responses to loading at the fibrillar level, and are likely to transform our understanding of the role of collagen fibril nano-mechanics in cartilage and other hydrated soft tissues. These methods can now be used to better understand cartilage in aging and other muscoskeletal diseases.

The main aim of this study to investigate the effectiveness of conceptual change texts oriented instruction accompanied with analogies over traditionally designed chemistry instruction on overcoming 10th grade students&rsquo / misconceptions, their understanding atoms and molecules concepts and attitude towards chemistry as a school subject . 45 tenth grades students from two classes of a chemistry course taught by the same teacher in Elmadag High School prticipated in the study that was carried out in 2004 &ndash / 2005 Fall semester . Two student groups participated in the study . One of them , called as Experimental group , was instructed with conceptual change text oriented instruction accompanied with analogies and the other one , called as Control group , was instructed with traditionally designed chemistry instruction over a period of two weeks . To investigate the effect of the treatment , Atoms and Molecules Concept Test and Attitude Scale Toward Chemistry as a school subject were administrated to all students in both groups at the begining and end of the the treatment . To evaluate students&rsquo / science process skills , Science Process Skills Test was administrated before treatment . ANCOVA and ANOVA were used to test the hypothesis of the study . The result of the study showed that students instructed with conceptual change text oriented instruction accompanied with analogies gained higher average scores in Atoms and Molecules Concept Test than students instructed by traditionally designed instruction . In addition , students in experiental group indicated a higher positive attitude toward chemistry as a school subject .The results also indicated science process skill was a stronger predictor for the achievement of atoms and molecules concepts. Strategies that were developed and results obtained for the present study may be used by science teachers to eliminate the students&rsquo / misconceptions about atoms and molecules concepts and provide better conceptual understanding of atoms and molecules.