Mössbauer studies of interactions between titanium atoms dissolved in iron

The room temperature ⁵⁷Fe Mössbauer spectra for binary iron-based solid solutions Fe_1???x Ti _x , with x in the range 0.010 ≤?x?≤ 0.045, were analysed in terms of binding energy E _b between two Ti atoms in the Fe-Ti system. The extrapolated values of E _b for x?= 0 were used for computation of enthalpy of solution of titanium in iron. The results were compared with that resulting from the Miedema’s model of alloys as well as those derived from the heat of formation of the system, obtained with both calorimetric measurements and theoretical calculations. The comparison shows that our Mössbauer spectroscopy findings are in a quite good agreement with all the other results mentioned above.     

Thermal,Raman and dielectric study of 0.5K0.5Bi0.5TiO3–0.5PbTiO3 ceramics

The 0.5K_0.5Bi_0.5TiO₃–0.5PbTiO₃ ceramics were prepared by following a standard solid-state method. The Raman, thermal and dielectric properties of these ceramics were investigated. The X-ray measurements showed that samples have single perovskite-type structure with tetragonal symmetry. Dielectric study revealed that the dielectric behaviour of the investigated ceramics is rather of normal ferroelectrics with large thermal hysteresis. The transition temperature observed by means of differential scanning calorimetry measurements is in good agreement with that obtained from dielectric study.     

Tunable dual-band liquid crystal based near-infrared perfect metamaterial absorber with high-loss metal

ABSTRACT

In this work, a tunable dual-band near-infrared perfect metamaterial absorber formed by combining a highly birefringent nematic liquid crystal with a nanoscale metamaterial cavity arranged in mirror symmetry is designed and numerically investigated. Electromagnetic simulations indicate that the absorbance greater than 99.4% may be achieved at 328 THz and 364 THz. Perfect absorbance results both form the use of highly lossy metal and the optimization of the metamaterial structure. In addition, absorbance of the metamaterial device can be substantially tuned both in terms of its magnitude and wavelength with the spectral tunability up to 8 THz by switching of liquid crystal alignment. The soft-matter-based metamaterial absorbers may pave a crucial role towards various active multifunctional systems working in the near-infrared range.     

Resonant equations with the Neumann p-Laplacian plus an indefinite potential

We consider a nonlinear Neumann problem driven by the p  -Laplacian plus an indefinite potential and a Carathéodory reaction which at ±∞ is resonant with respect to any nonprincipal variational eigenvalue of the differential operator. Using critical point theory and Morse theory (critical groups), we show that the problem has at least three nontrivial smooth solutions, two of which have constant sign. In the process we prove some results of independent interest concerning the unique continuation property of eigenfunctions and the critical groups at infinity of a C¹$C^1$-functionals.     

Chimera Spectrum Diagnostics for Peptides Using Two-Dimensional Partial Covariance Mass Spectrometry

The rate of successful identification of peptide sequences by tandem mass spectrometry (MS/MS) is adversely affected by the common occurrence of co-isolation and co-fragmentation of two or more isobaric or isomeric parent ions. This results in so-called `chimera spectra’, which feature peaks of the fragment ions from more than a single precursor ion. The totality of the fragment ion peaks in chimera spectra cannot be assigned to a single peptide sequence, which contradicts a fundamental assumption of the standard automated MS/MS spectra analysis tools, such as protein database search engines. This calls for a diagnostic method able to identify chimera spectra to single out the cases where this assumption is not valid. Here, we demonstrate that, within the recently developed two-dimensional partial covariance mass spectrometry (2D-PC-MS), it is possible to reliably identify chimera spectra directly from the two-dimensional fragment ion spectrum, irrespective of whether the co-isolated peptide ions are isobaric up to a finite mass accuracy or isomeric. We introduce ‘3-57 chimera tag’ technique for chimera spectrum diagnostics based on 2D-PC-MS and perform numerical simulations to examine its efficiency. We experimentally demonstrate the detection of a mixture of two isomeric parent ions, even under conditions when one isomeric peptide is at one five-hundredth of the molar concentration of the second isomer.     

Silicon solar cells with Al2O3 antireflection coating

The paper presents the possibility of using Al₂O₃ antireflection coatings deposited by atomic layer deposition ALD. The ALD method is based on alternate pulsing of the precursor gases and vapors onto the substrate surface and then chemisorption or surface reaction of the precursors. The reactor is purged with an inert gas between the precursor pulses. The Al₂O₃ thin film in structure of the finished solar cells can play the role of both antireflection and passivation layer which will simplify the process. For this research 50×50 mm monocrystalline silicon solar cells with one bus bar have been used. The metallic contacts were prepared by screen printing method and Al₂O₃ antireflection coating by ALD method. Results and their analysis allow to conclude that the Al₂O₃ antireflection coating deposited by ALD has a significant impact on the optoelectronic properties of the silicon solar cell. For about 80 nm of Al₂O₃ the best results were obtained in the wavelength range of 400 to 800 nm reducing the reflection to less than 1%. The difference in the solar cells efficiency between with and without antireflection coating was 5.28%. The LBIC scan measurements may indicate a positive influence of the thin film Al₂O₃ on the bulk passivation of the silicon.     

Photodynamics of the bacteriochlorophyll-carotenoid system. 2. Influence of central metal,solvent and beta-carotene on photobleaching of bacteriochlorophyll derivatives

Bacteriochlorophyll (BChl) derivatives (with central Mg replaced by metal "M") ([M]-BChl with M = 2H, Mg, Zn, Pd, Cu) have been investigated for their photodynamic capacity and stability toward photodegradation in organic solvents and aqueous micellar solution. A protocol has been developed for screening new sensitizers. BChl and [Zn]-BChl are efficient sensitizers, but they are also quickly degraded by the reactive oxygen species (ROS) produced by autosensitization, as well as by hetero-sensitization with 17(4)-methyl-13(2)-demethoxycarbonyl-pheophorbide a (MPP). Photostable [Cu]-BChl is a poor sensitizer, whereas [Pd]-BChl and bacteriopheophytin a are not only very efficient sensitizers but are also very stable toward ROS. beta-Carotene is no efficient physical quencher of ROS in the system; rather, it acts as a photochemical quencher that competes with [M]-BChl and undergoes photooxygenation at high rates. Photolability seems to depend on the pigment oxidation potential and, in parallel, on the presence of central metals preferring coordination numbers higher than 4, whereas photodynamic capacity depends on long excited state life-times of the pigment or efficient intersystem crossing (or both).