Morphological and Functional Modifications of Optical Thin Films for Space Applications Irradiated with Low-Energy Helium Ions.

Future space missions will operate in increasingly hostile environments, such as those in low-perihelion solar orbits and Jovian magnetosphere. This exploration involves the selection of optical materials and components resistant to the environmental agents. The conditions in space are reproduced on ground through the use of ion accelerators. The effects of He particles coming from the solar wind impinging on a gold thin film have been systematically investigated, considering absorbed doses compatible with the duration of the European Space Agency Solar Orbiter mission. Structural and morphological changes have been proved to be dependent not only on the dose but also on the irradiation flux. A predictive model of the variation of thin film reflectance has been developed for the case of lower flux irradiation. The results are discussed regarding reliability and limitations of laboratory testing. The outcomes are important to address the procedures for the space qualification tests of optical coatings.

Chaperone patterns in vernal keratoconjunctivitis are distinctive of cell and Hsp type and are modified by inflammatory stimuli.

BACKGROUND: Vernal keratoconjunctivitis (VKC) is a severe ocular allergy with pathogenic mechanism poorly understood and no efficacious treatment. The aims of the study were to determine quantities and distribution of Hsp chaperones in the conjunctiva of VKC patients and assess their levels in conjunctival epithelial and fibroblast cultures exposed to inflammatory stimuli. METHODS: Hsp10, Hsp27, Hsp40, Hsp60, Hsp70, Hsp90, Hsp105, and Hsp110 were determined in conjunctiva biopsies from nine patients and nine healthy age-matched normal subjects, using immunomorphology and qPCR. Conjunctival epithelial cells and fibroblasts were cultured and stimulated with IL-1ß, histamine, IL-4, TNF-α, or UV-B irradiation, and changes in Hsp levels were determined by Western blotting. RESULTS: Hsp27, Hsp40, Hsp70, and Hsp90 levels increased in the patients' conjunctiva, whereas Hsp10, Hsp60, Hsp100, and Hsp105 did not. Double immunofluorescence demonstrated colocalization of Hsp27, Hsp40, Hsp70, and Hsp90 with CD68 and tryptase. Testing of cultured conjunctival cells revealed an increase in the levels of Hsp27 in fibroblasts stimulated with IL-4; Hsp40 in epithelial cells stimulated with IL-4 and TNF-α and in fibroblasts stimulated with IL-4, TNF-α, and IL-1ß; Hsp70 in epithelial cells stimulated with histamine and IL-4; and Hsp90 in fibroblasts stimulated with IL-1ß, TNF-α, and IL-4. UV-B did not induce changes. CONCLUSIONS: VKC conjunctiva displays distinctive quantitative patterns of Hsps as compared with healthy controls. Cultured conjunctival cells respond to cytokines and inflammatory stimuli with changes in the Hsps quantitative patterns. The data suggest that interaction between the chaperoning and the immune systems drives disease progression.

Analysis of buried interfaces in multilayer mirrors using grazing incidence extreme ultraviolet reflectometry near resonance edges.

Accurate measurements of optical properties of multilayer (ML) mirrors and chemical compositions of interdiffusion layers are particularly challenging to date. In this work, an innovative and nondestructive experimental characterization method for multilayers is discussed. The method is based on extreme ultraviolet (EUV) reflectivity measurements performed on a wide grazing incidence angular range at an energy near the absorption resonance edge of low-Z elements in the ML components. This experimental method combined with the underlying physical phenomenon of abrupt changes of optical constants near EUV resonance edges enables us to characterize optical and structural properties of multilayers with high sensitivity. A major advantage of the method is to perform detailed quantitative analysis of buried interfaces of multilayer structures in a nondestructive and nonimaging setup. Coatings of Si/Mo multilayers on a Si substrate with period d=16.4 nm, number of bilayers N=25, and different capping structures are investigated. Stoichiometric compositions of Si-on-Mo and Mo-on-Si interface diffusion layers are derived. Effects of surface oxidation reactions and carbon contaminations on the optical constants of capping layers and the impact of neighboring atoms' interactions on optical responses of Si and Mo layers are discussed.