In-situ spectroscopy of intrinsic Bi2Te3 topological insulator thin films and impact of extrinsic defects

Combined in-situ x-ray photoemission spectroscopy, scanning tunnelling spectroscopy and angle resolved photoemission spectroscopy of molecular beam epitaxy grown Bi2Te3 on lattice mismatched substrates reveal high quality stoichiometric thin films with topological surface states without a contribution from the bulk bands at the Fermi energy. The absence of bulk states at the Fermi energy is achieved without counter doping. We observe that the surface morphology and electronic band structure of Bi2Te3 are not affected by in-vacuo storage and exposure to oxygen, whereas major changes are observed when exposed to ambient conditions. These films help define a pathway towards intrinsic topological devices.Comment: 8 pages, 5 figure

Interfacial fracture energy and the toughness of composites

The premises upon which prevailing composite toughness theories are based are discussed in the light of observed strength variations in boron-epoxy composites with differing shear strengths of the interfacial bond. None of the extant toughness theories (pull-out, debonding, stress redistribution) successfully predicts the work of fracture of the boronepoxy system. However, incorporation of the work to create new surfaces into the total toughness analysis gives better agreement with experiment, and work of fracture predictions for other sytems, such as carbon-polyester, can also be modified. The approach is more generalized than the Outwater/Murphy debonding explanation for toughness, which in the way usually presented only applies when the filament fracture strain is greater than the matrix fracture strain. The present analysis suggests how to tailor the interfacial shear strength in order to obtain a reasonable toughness yet still maintain strengths of the order of the rule of mixtures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44787/1/10853_2004_Article_BF00737846.pd

Proportional mouse model for aerosol infection by influenza

Aims: The aim of this study was to demonstrate a prototype tool for measuring infectivity of an aerosolized human pathogen – influenza A/PR/8/34 (H1N1) virus – using a small-animal model in the Controlled Aerosol Test System (CATS). Methods and Results: Intranasal inoculation of nonadapted H1N1 virus into C57BL, BALB/c and CD-1 mice caused infection in all three species. Respiratory exposure of CD-1 mice to the aerosolized virus at graduated doses was accomplished in a modified rodent exposure apparatus. Weight change was recorded for 7 days postexposure, and viral populations in lung tissue homogenates were measured post mortem by DNA amplification (qRT-PCR), direct fluorescence and microscopic evaluation of cytopathic effect. Plots of weight change and of PCR cycle threshold vs delivered dose were linear to threshold doses of ~40 TCID50 and ~12 TCID50, respectively. Conclusions: MID50 for inspired H1N1 aerosols in CD-1 mice is between 12 and 40 TCID50; proportionality to dose of weight loss and viral populations makes the CD-1 mouse a useful model for measuring infectivity by inhalation. Significance and Impact of the Study: In the CATS, this mouse–virus model provides the first quantitative method to evaluate the ability of respiratory protective technologies to attenuate the infectivity of an inspired pathogenic aerosol