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To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation. [ABSTRACT FROM AUTHOR]

The linear and nonlinear optical properties of one-dimensional photonic crystals containing ZnO defects were studied by linear absorption spectroscopy and the femtosecond Z-scan technique. Photonic crystals containing ZnO defects, (Ta2O5/SiO2)5/ZnO/(SiO2/Ta2O5)5, were prepared using electron-beam deposition and magnetron sputtering. The transmission spectra of these photonic crystals revealed a defect mode resonance and a broad photonic band gap. The observed transmission spectra could be described by applying the optical transfer matrix formalism to the multilayer structure. When compared with the Z-scan curve of the ZnO film, that of the resonant photonic crystal exhibited a larger transmittance dip. The enhancement of the nonlinear absorption in the resonant photonic crystal is due to the strong confinement of the optical field. [ABSTRACT FROM AUTHOR]

Atmospheric-pressure A r plasma jets are known to be detrimental to Cordyceps pruinosa spores. However, it is not clear what kinds of reactive species are more effective with regard to fungal cell death. Herein, we study which reactive species plays pivotal roles in the death of fungal spores using an electric shock-free, atmospheric-pressure air plasma jet, simply called soft plasma jet. Plasma treatment significantly reduced the spore viability and damaged fungal DNA. As observed from the circular dichroism spectra, scanning electron microscope images, and flow cytometric measurements, cell wall integrity was decreased by reactive oxygen and nitrogen species (RONS) from the plasma itself and the plasma-activated water. Consequently, degradation of the spore cell wall allows RONS from the plasma to reach the intracellular components. Such plasma-induced intracellular RONS can attack spore DNA and other intracellular components, as confirmed by electrophoresis analysis and phosphorylated histone measurement. In addition, weakening of the spore cell wall allowed for the loss of intracellular components, which can lead to cell death. Plasma radicals were investigated by measuring the optical emission spectrum of the soft plasma jet, and intracellular reactive oxygen species were confirmed by measuring the fluorescence of 2′, 7′-dichlorodihydrofluorescein-diacetate ( H 2 D C F - D A )-stained spores. The soft plasma jet generated considerable amounts of H 2 O 2 and N O x but a very small number of O H radicals as compared to the atmospheric-pressure A r plasma jet; this indicates that plasma-induced long-lived reactive species ( H 2 O 2 and N O x ) play an important role in the weakening of spore cell walls and cell death. [ABSTRACT FROM AUTHOR]

A magnetic grating with a periodicity of 2 μm was generated by selective crystallization of an amorphous Cu2MnSn thin film using femtosecond laser pulses. By irradiating the amorphous Cu2MnSn thin film with two-beam interference pattern of femtosecond laser pulses, alternating bands of ferromagnetic and paramagnetic phases were produced. The crystallized region was composed of ferromagnetic Cu2MnSn grains, whereas the amorphous region remained paramagnetic. Because crystallized Cu2MnSn is the only ferromagnetic phase that can be produced by heat-treatment of the amorphous Cu2MnSn thin film, a magnetic grating with high definition was produced. Moreover, the periodicity of the modulated structure can be reduced down to a submicrometer scale and extended to two dimensions so that the technique could be potentially utilized for magnetic patterning. [ABSTRACT FROM AUTHOR]

Femtosecond laser-interference induced amorphization (FLIA) was used to form a spatially periodic magnetic structure by selectively amorphizing the surface of bulk Co2MnSi. Regularly spaced alternating lines with a periodicity of 2 μm were produced by FLIA. Magnetic force microscopy of the samples clearly revealed one-dimensional periodic magnetic domains resulting from the modulated surface structure which was confirmed by transmission electron microscopy. The periodicity of the modulated structure can be further decreased or the process can be modified to write two-dimensional pattern so that the resulting magnetic structure can be potentially utilized for a permanent magnetic identification. [ABSTRACT FROM AUTHOR]

Femtosecond laser-interference crystallization (FLIC) was used to form a spatially periodic magnetic structure by selectively crystallizing a paramagnetic amorphous Co2MnSi thin film. Regularly spaced alternating lines of polycrystalline and microcrystalline regions with a periodicity of 2 μm were produced by FLIC. The crystalline region composed of ∼100-nm-sized grains contained a nonequilibrium ferromagnetic phase intermixed with β-Mn. The areas between the crystallized lines also received sufficient energy, crystallizing into a microcrystalline state with its grain size ranging from 1 to 5 nm. The magnetic force microscopy of the samples clearly revealed the one-dimensional periodic magnetic domains resulting from the modulated microstructure. [ABSTRACT FROM AUTHOR]

Tricyano benzene derivatives having large second-order nonlinear optical characteristics were studied.