Stress-activated protein kinase (SAPK) pathways are evolutionarily conserved signaling modules that orchestrate protective responses to adverse environmental conditions. However, under certain conditions, their activation can be deleterious. Thus, activation of the c-Jun N-terminal kinase (JNK) SAPK pathway exacerbates a diverse set of pathologies, many of which are typical of old age. The contexts determining whether the outcome of JNK signaling is protective or detrimental are not fully understood. Here, we show that the age of an animal defines such a context. The Caenorhabditis elegans JNK homolog, KGB-1, provides protection from heavy metals and protein folding stress in developing animals. However, we found that with the onset of adulthood, KGB-1 activity becomes detrimental, reducing stress resistance and lifespan. Genetic analyses coupled with fluorescent imaging linked this phenotypic switch to age-dependent antagonistic modulation of DAF-16/FOXO: KGB-1 activation enhanced DAF-16 nuclear localization and transcriptional activity during development but decreased it in adults. Epistasis analyses showed that DAF-16 was necessary and sufficient to explain some of the kgb-1-dependent detrimental phenotypes, but not all. The identification of early adulthood as a point following which the contribution of KGB-1 activity reverses from beneficial to detrimental sheds new light on the involvement of JNK signaling in age-related pathologies. Furthermore, the age-dependent reversal has intriguing implications for our understanding of aging.

Diffraction of light beams from the phase steps due to the abrupt/sharp changes in the boundary of step leads to Fresnel fringes whose visibility and intensity profile depend on the change of the step height or light incident angle. The visibility has been utilized in measurements of different physical quantities. In this paper, for the first time to our knowledge by introducing the fitting method as a fast method we show that by fitting the theoretical intensity distributions on the experimental intensity profiles of the light diffracted from a step at different incident angles, one can specify the step height with few nanometers precision. In addition, we show that this approach provides accurate film thickness in a broad range of thicknesses using modest instrumentation. Furthermore, based on Fresnel diffraction from phase step we have manufactured and trademarked an optical device for measuring thickness of thin films.

Mirage is a fascinating phenomenon that has attracted many scientists to report their observations and descriptions about it. There are two different approaches to mirage formation. The more popular one is attributed to total internal reflection that occurs in the near ground air layers on hot sunny days. According to the other approach, mirage is an image in a rough surface that is observed at grazing angles of incidence. Most of the existing descriptions are qualitative and some include calculations based on guessing temperature change with no concrete experiments. In this report, first we show that Fermat's principle also concerns the wave nature of light and covers the constructive and destructive interference that is essential for image formation. Then, we provide a brief review of the image formation theory in a rough plane and demonstrate by experiments in the lab and deserts that the temperature gradient in the near ground air layers does not lead to mirage formation.

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