97 research outputs found
Molecular identification of a phytoplasma infecting grapevine in the Republic of Macedonia
Phytoplasmas from the ribosomal subgroup 16SrXII-A (stolbur) were identified by PCR and RFLP analyses of 16S rRNA gene and elongation factor-Tu phytoplasma gene (tuf) in symptomatic grapevines from the Veles and Skopje areas in Macedonia. Two methods were used for nucleic acid extraction. Amplification and RFLP results of 16S rDNA were not influenced by the method used, but RFLP patterns of tuf gene revealed additional bands if a less time consuming method was applied. The possible origin of these bands is discussed. This is the first report of the presence of the stolbur phytoplasma in cvs Chardonnay and Vranac in Macedonia.
Photoinduced suppression of the ferroelectric instability in PbTe
The interactions between electrons and phonons drive a large array of
technologically relevant material properties including ferroelectricity,
thermoelectricity, and phase-change behaviour. In the case of many group IV-VI,
V, and related materials, these interactions are strong and the materials exist
near electronic and structural phase transitions. Their close proximity to
phase instability produces a fragile balance among the various properties. The
prototypical example is PbTe whose incipient ferroelectric behaviour has been
associated with large phonon anharmonicity and thermoelectricity. Experimental
measurements on PbTe reveal anomalous lattice dynamics, especially in the soft
transverse optical phonon branch. This has been interpreted in terms of both
giant anharmonicity and local symmetry breaking due to off-centering of the Pb
ions. The observed anomalies have prompted renewed theoretical and
computational interest, which has in turn revived focus on the extent that
electron-phonon interactions drive lattice instabilities in PbTe and related
materials. Here, we use Fourier-transform inelastic x-ray scattering (FT-IXS)
to show that photo-injection of free carriers stabilizes the paraelectric
state. With support from constrained density functional theory (CDFT)
calculations, we find that photoexcitation weakens the long-range forces along
the cubic direction tied to resonant bonding and incipient ferroelectricity.
This demonstrates the importance of electronic states near the band edges in
determining the equilibrium structure.Comment: 9 page, 3 figure
Understanding and improving electroluminescence in mill-ground ZnS : Cu,Cl phosphors
Abstract We demonstrate that lightly milled ZnS : Cu,Cl phosphors produce AC electroluminescence (EL) emission in devices half as thick and produce up to 5 times the light output as the thinnest devices made with unground phosphors. We also establish minimum and maximum bounds on micro-milling conditions for producing powders that are still viable for AC EL. To understand the cause of the minimum size, we report extended x-ray absorption fine structure (EXAFS) measurements on phosphors sorted by particle size. The EXAFS data show that grinding preferentially damages the initially embedded CuS nano-precipitate. This suggests that grinding cleaves the ZnS : Cu through the embedded CuS nano-precipitates, leaving the CuS nano-precipitates on the surface to be further broken apart by continued grinding, eventually reducing the effectiveness of the CuS-induced electric field enhancement
Local terahertz field enhancement for time-resolved x-ray diffraction
We report local field strength enhancement of single-cycle terahertz (THz) pulses in an ultrafast time-resolved x-ray diffraction experiment. We show that patterning the sample with gold microstructures increases the THz field without changing the THz pulse shape or drastically affecting the quality of the x-ray diffraction pattern. We find a five-fold increase in THz-induced x-ray diffraction intensity change in the presence of microstructures on a SrTiO3 thin-film sample
Steganography Method Using Hartley Transform
Kozin A. Steganography Method Using Hartley Transform / Alexander Kozin, Olga Papkovskaya, Mariia Kozina // Modern Problems of Radio Engineering, Telecommunications, and Computer Science : XIIIth 2016 International Conference (Lviv-Slavsko, February 23 – 26, 2016). - Lviv, 2016. - p. 473 -475. = Сучасні проблеми радіоелектроніки, телекомунікацій, комп'ютерної інженерії : матеріали Міжнар. конф.TCSET’2016 ( Львів-Славсько, 23-26 лютого 2016 р.). - Львів, 2016. - с. 473-475.This paper presents the method of
steganography that organizes a covert communication
channel, by embedding the additional information in the
frequency domain. The proposed method of embedding
the additional information in the coefficients of the
discrete Hartley transforms, due to unavailability of a
complex data structures. It has the symmetry of the
formulas the direct and the inverse transform that's why it
ensures high computational efficiency in the processing of
real data type
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