A spectroscopy approach to the study of virus infection in the endophytic fungus Epichloë festucae

<p>Abstract</p> <p>Background</p> <p>In this work we propose a rapid method based on visible and near-infrared (Vis-NIR) spectroscopy to determine the occurrence of double-stranded RNA (dsRNA) viruses in <it>Epichloë festucae </it>strains isolated from <it>Festuca rubra </it>plants. In addition, we examined the incidence of infections by <it>E. festucae </it>in populations of <it>F. rubra </it>collected in natural grasslands of Western Spain.</p> <p>Methods</p> <p>Vis-NIR spectra (400-2498 nm) from 124 virus-infected and virus-free <it>E. festucae </it>isolates were recorded directly from ground and freeze-dried mycelium. To estimate how well the spectra for uninfected and infected fungal samples could be differentiated, we used partial least-squares discriminant analysis (PLS1-DA) and several data pre-treatments to develop calibration models.</p> <p>Results</p> <p>Applying the best regression model, obtained with two sampling years and using standard normal variate (SNV) combined with first derivative transformation to a new validating data set (42 samples), we obtained a correct classification for 75% of the uninfected isolates and up to 86% of the infected isolates.</p> <p>Conclusions</p> <p>The results obtained suggest that Vis-NIR spectroscopy is a promising technology for detection of viral infections in fungal samples when an alternative faster approach is desirable. It provides a tool adequately exact and more time- and cost-saving than the conventional reference analysis.</p

Percutaneous imaging-guided interventions for acute biliary disorders in high surgical risk patients

AIM: To evaluate the efficacy of percutaneous imaging-guided biliary interventions in the management of acute biliary disorders in high surgical risk patients

Photoorientation of a liquid crystalline polyester with azobenzene side groups:1. Effects of irradiation with linearly polarized blue light

The photoorientation process in a polyester with 4-cyano-4'-alkoxyazobenzene side group and long methylene spacers in the side and the main-chain was studied as a function of irradiation with linearly polarized light of 488 nm under systematic variation of the power density and temperature. This model polymer is characterized by liquid crystallinity (g 24 S-X 26 S-A 34 n 47 i) and a strong aggregation tendency. The photoorientation is cooperative, i.e., the orientation of the photochromic side group induces the alignment of the ester unit (which is a part of the main-chain) and both methylene segments in the side- and main-chain. The very high values of the normalized linear dichroism up to 0.8 and the birefringence (above 0.3) are due to the interaction of photoorientation and thermotropic self-organization. The induction of anisotropy shows a pronounced dependence on the power density and the working temperature. This is related to the thermal properties of the LC polymer and the resulting ordering behavior. Surprisingly, the photoorientation process, is not restricted by J-aggregation of the azobenzene groups even at low power densities. The highest anisotropy at 27 T (slightly above T-g) is achieved by a low power density (1 mW/cm(2) and dose of 0.5 mW/cm(2)s). Higher power densities result in a decrease of the maximum dichroism and, finally, the initially induced small anisotropy is erased during continuing light exposure. At a constant high power density of about 700 mW/cm(2), the saturation value of the dichroism first increases with the irradiation temperature, then passes through a maximum of about 0.8 at 18 degreesC and finally the film is transferred to the isotropic state at 27 T. Both effects indicate a significant thermal effect of the laser beam on the polymer film. Taking into account the thermal properties of the investigated polymer it is demonstrated that the photoinduced anisotropy depends,,strongly on the irradiation conditions