Detection and Identification of Microorganisms in Mixed Cultures by Nanoparticle-Induced Nanospr Enhanced FTIR Spectroscopy and Chemometrics

Routine identification of pathogenic microorganisms predominantly based on nutritional and biochemical tests is a time-consuming process; the delay may lead to fatal consequences at times. In this work, nanoparticle-induced nanoSPR enhanced IR spectroscopy was used in conjunction with a background elimination data processing algorithm to directly identify microorganisms in mixed cultures. It was demonstrated that the microbial composition of mixtures of different E. coli strains could be identified with 100% accuracy. The procedure was also applied to determine the presence or absence of pathogenic microorganisms in a simple but real food matrix (apple juice). Results indicated that microorganisms in a cocktail of up to eight different species suspended in an apple juice matrix could be identified for its presence or absence with 100% accuracy

Impact of high-frequency pumping on anomalous finite-size effects in three-dimensional topological insulators

Lowering of the thickness of a thin-film three-dimensional topological insulator down to a few nanometers results in the gap opening in the spectrum of topologically protected two-dimensional surface states. This phenomenon, which is referred to as the anomalous finite-size effect, originates from hybridization between the states propagating along the opposite boundaries. In this work, we consider a bismuth-based topological insulator and show how the coupling to an intense high-frequency linearly polarized pumping can further be used to manipulate the value of a gap. We address this effect within recently proposed Brillouin-Wigner perturbation theory that allows us to map a time-dependent problem into a stationary one. Our analysis reveals that both the gap and the components of the group velocity of the surface states can be tuned in a controllable fashion by adjusting the intensity of the driving field within an experimentally accessible range and demonstrate the effect of light-induced band inversion in the spectrum of the surface states for high enough values of the pump.Comment: 6 pages, 3 figure