The objective of this paper was to investigate the influence of UV irradiation on collagen D-band periodicity by using the AFM imaging and nanoindentation methods. It is well known than UV irradiation is one of the main factors inducing destabilization of collagen molecules. Due to the human's skin chronic exposure to sun light, the research concerning the influence of UV radiation on collagen is of great interest. The impact of UV irradiation on collagen can be studied in nanoscale using Atomic Force Microscopy (AFM). AFM is a powerful tool as far as surface characterization is concerned, due to its ability to relate high resolution imaging with mechanical properties. Hence, high resolution images of individual collagen fibrils and load-displacement curves on the overlapping and gap regions, under various time intervals of UV exposure, were obtained. The results demonstrated that the UV rays affect the height level differences between the overlapping and gap regions. Under various time intervals of UV exposure, the height difference between overlaps and gaps reduced from ~3.7 nm to ~0.8 nm and the fibril diameters showed an average of 8-10% reduction. In addition, the irradiation influenced the mechanical properties of collagen fibrils. The Young's modulus values were reduced per 66% (overlaps) and 61% (gaps) compared to their initial values. The observed alterations on the structural and the mechanical properties of collagen fibrils are probably a consequence of the polypeptide chain scission due to the impact of the UV irradiation.
Objective: The development of a new non-intrusive optical system for remotely measuring acoustic startle reflex (ASR) in humans. Approach: The eye reflex movement during an acoustic stimulation session is recorded through a high-speed digital camera. The eyes region is isolated by the rest of the face by an advanced pyramid-like feature detection algorithm, which greatly reduces the number of false positives. A separate Lucas–Kanade optical flow routine is designed for the eyeblink movement detection and the startle eyeblink reflex (SEBR) curve extraction. Image masking is implemented for the elimination of unwanted artifacts caused mainly by voluntary eye movement. The proposed system was tested along with a valid EMG system on a sample of 32 healthy randomly selected adults, and the results were compared in order to measure the system’s degree of reliability. Main results: To assess the proposed method’s validity the EMG data was used as a benchmark. The results showed strong correlation between EMG and Camera acquired results, which proves the validity of the proposed method. Furthermore, by comparing the response probability and the signal to noise ratio (SNR) for the two techniques, we proved that the proposed method can surpass the traditional EMG system in terms of accuracy and reliability. Significance: The proposed technique presents a simple, robust and reliable non-intrusive means of measuring ASR in humans, with the potential of future implementation on various ASR psychophysiology experiments, such as the study of PPI.
Electromagnetic radiation can be classified into two major types depending on its ability to detach electrons from atoms: ionising and non-ionising. The aforementioned categorization is significant due to the effects of ionising radiation on human tissue (e.g. carcinogenesis). However, many students around the globe cannot distinguish these two types of electromagnetic radiation and as a result significant misconceptions arise regarding this topic (for example radiation emitted by mobile phones is considered by many students as ionising). Hence, in this paper a teaching approach specifically designed and implemented for the secondary education level is presented, based on the absorbed energy distribution by atoms/molecules in each radiation type. More specifically, the number of atoms/molecules that absorb equal doses of energy per unit mass can be used in order to explain the difference in the effects caused by the two abovementioned radiation types. Also, two analogies from classical mechanics are presented to provide a full insight into the energy distribution concept from a teaching perspective.
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