Fabrication of Insoluble Elastin by Enzyme-Free Cross-Linking.

Elastin is an essential extracellular matrix protein that enables tissues and organs such as arteries, lungs, and skin, which undergo continuous deformation, to stretch and recoil. Here, an approach to fabricating artificial elastin with close-to-native molecular and mechanical characteristics is described. Recombinantly produced tropoelastin are polymerized through coacervation and allysine-mediated cross-linking induced by pyrroloquinoline quinone (PQQ). A technique that allows the recovery and repeated use of PQQ for protein cross-linking by covalent attachment to magnetic Sepharose beads is developed. The produced material closely resembles natural elastin in its molecular, biochemical, and mechanical properties, enabled by the occurrence of the cross-linking amino acids desmosine, isodesmosine, and merodesmosine. It possesses elevated resistance against tryptic proteolysis, and its Young's modulus ranging between 1 and 2 MPa is similar to that of natural elastin. The approach described herein enables the engineering of mechanically resilient, elastin-like materials for biomedical applications.

Relation of optical properties and femtosecond laser damage resistance for Al2O3/AlF3 and Al2O3/SiO2 composite coatings.

We report on the realization of aluminum oxyfluoride thin films and alumina/silica mixture coatings with different ratios by ion beam sputtering. The atomic compositions quantified by energy dispersive x-ray spectroscopy are correlated with the optical properties calculated from spectrophotometry and laser calorimetry measurements. Furthermore, the femtosecond laser damage resistance (τ=400 fs) of single layers is investigated in the infrared at 1030 nm and in the ultraviolet at 343 nm wavelengths. Experimental results on the wavelength scaling of the laser-induced damage threshold for oxyfluoride and oxide composite coatings are presented.

Laser-induced damage in composites of scandium, hafnium, aluminum oxides with silicon oxide in the infrared.

The laser-induced damage of mixtures of Sc2O3, HfO2, Al2O3 with SiO2 has been characterized in the infrared for both nanosecond and subpicosecond pulses. Laser-induced damage thresholds (LIDTs) are reported and discussed versus band gap for different compositions. The distributions versus fluence of nanosecond damage precursor densities are extracted fitting damage probability curves. Two models are used: first, a statistical approach, i.e., direct calculation of damage precursor density from damage probability, and second a thermal model based on absorption of initiator. The results show a good agreement. The nature, shape, and size of these precursors are discussed. The critical temperature in the thermal model is dependent on the band gap energy.

Laser damage resistance of ion-beam sputtered Sc2O3/SiO2 mixture optical coatings.

We report on the correlation between the laser damage resistance, the optical and the physical properties of Sc(2)O(3)/SiO(2) mixture coatings. Several sets of samples with ten different mixture ratios have been prepared by ion-beam sputtering. The atomic compositions of the mixture thin films are quantified employing x-ray photoelectron spectroscopy depth profiles. Laser-induced damage thresholds are determined with single subpicosecond pulses (500 fs) at 1030 nm. Furthermore, Son1 multishot measurements are realized in the ultraviolet wavelength range (355 nm) at pulse durations of 5 ns. In addition, the influence of two different substrate polishing qualities on the radiation resistance of the composite thin films is discussed.

Role of two-photon absorption in Ta2O5 thin films in nanosecond laser-induced damage.

Laser-induced damage in the nanosecond domain has been connected to the heating and breakdown of local defects within the thin film and the various interfaces. Within the femtosecond regime, the damaging events can be traced back to multiphoton-based excitation into the conduction band. When critical electron density is exceeded, an optical breakdown will occur. In this Letter we report on evidence that two-photon absorption also significantly triggers laser-induced damage in Ta(2)O(5) thin films at 532 nm and 8 ns pulse duration. For experimental verification, single layers of Ta(2)O(5)/SiO(2) mixtures have been analyzed.

Femtosecond laser damage resistance of oxide and mixture oxide optical coatings.

We report on the laser damage resistance of ion beam-sputtered oxide materials (Al2O3, Nb2O5, HfO2, SiO2, Ta2O5, ZrO2) and mixtures of Al2O3-SiO2, Nb2O5-SiO2, HfO2-SiO2, Ta2O5-SiO2, and ZrO2-SiO2, irradiated by single 500 fs pulses at 1030 nm. Laser-induced damage threshold (LIDT), refractive index, and bandgaps of the single-layer coatings are measured. For pure oxide materials a linear evolution of the LIDT with bandgap is observed. The results are in accordance with our simulations based on photo-ionization and avalanche-ionization. In the case of mixtures, however, deviations from the previous behaviors are evidenced. The evolution of the LIDT as a function of the refractive index is analyzed, and an empirical description of the relation between refractive index and LIDT is proposed.

Mixed oxide coatings for optics.

Material mixtures offer new possibilities for synthesizing coating materials with tailored optical and mechanical properties. We present experimental results on mixtures of HfO2, ZrO2, and Al2O3, pursuing applications in UV coating technology, while the mixtures are prepared by magnetron sputtering, ion beam sputtering, plasma ion-assisted deposition (PIAD), and electron beam evaporation without assistance. The properties investigated include the refractive index, optical gap, thermal shift, and mechanical stress. The first high reflectors for UV applications have been deposited by PIAD.