Comparison of microwave properties of YBCO films on MgO and LaAlO3 substrates

To obtain low loss and better performance of high temperature superconducting (HTS) microwave devices, higher quality HTS thin films are required. As it is well known, properties of HTS films and effects of temperature, frequency and microwave power on the properties depend on the type of substrate used and the method of deposition. YBa2Cu3O7−δ (YBCO) films on lanthanum aluminate (LAO) are considered to have lowest losses, and are commonly used for HTS planar filters for cellular phone base stations. We have measured the surface resistance (Rs) of high quality YBCO thin films, deposited on LAO and MgO substrates, as a function of frequency, temperature and microwave power to assess the quality of YBCO films on the lower cost MgO substrates for possible applications in communication systems

Microwave properties and microstructure of Y1Ba2Cu3O7 thin films

The microwave properties of high-J(c) (~10⁶ A cm⁻²) c-axis Y₁Ba₂Cu₃O₇ this films on MgO(100) substrates were investigated as a function of the film microstructure. Measurements at 77 K, using a sapphire dielectric resonator operated in the TE₀₁₁ mode, show that the microwave surface resistance,R(s), at 10 GHz increases from 0.8 mΩ for very smooth films to 3–4 mΩ for films with large scale microstructural defects such as outgrowths and holes or pits. The unloaded quality factor Q(u) decreases from about 96,000 to below 50,000

Alzheimer's-Causing Mutations Shift Aβ Length by Destabilizing γ-Secretase-Aβn Interactions

Alzheimer's disease (AD)-linked mutations in Presenilins (PSEN) and the amyloid precursor protein (APP) lead to production of longer amyloidogenic Aβ peptides. The shift in Aβ length is fundamental to the disease; however, the underlying mechanism remains elusive. Here, we show that substrate shortening progressively destabilizes the consecutive enzyme-substrate (E-S) complexes that characterize the sequential γ-secretase processing of APP. Remarkably, pathogenic PSEN or APP mutations further destabilize labile E-S complexes and thereby promote generation of longer Aβ peptides. Similarly, destabilization of wild-type E-S complexes by temperature, compounds, or detergent promotes release of amyloidogenic Aβ. In contrast, E-Aβn stabilizers increase γ-secretase processivity. Our work presents a unifying model for how PSEN or APP mutations enhance amyloidogenic Aβ production, suggests that environmental factors may increase AD risk, and provides the theoretical basis for the development of γ-secretase/substrate stabilizing compounds for the prevention of AD.status: publishe