Diphenylalanine (FF) peptide nanotubes (PNTs) present a unique class of selfassembled functional biomaterials owing to a wide range of useful properties including nanostructural variability, mechanical rigidity, and chemical stability. In addition, a strong piezoelectric activity has been recently observed paving the way to their use as nanoscale sensors and actuators. In this work, we fabricated both horizontal and vertical FF PNTs and examined their optical second harmonic generation and local piezoresponse as a function of temperature. The measurements show gradual decrease of polarization with increasing temperature accompanied by irreversible phase transition into another crystalline phase at about 140-150 ºC. The results are corroborated by the molecular dynamic simulations predicting order-disorder phase transition into centrosymmetric (possibly, orthorhombic) phase with antiparallel polarization orientation in neighboring FF rings. Partial piezoresponse hysteresis indicates incomplete polarization switching due to high coercive field in FF PNTs.
Tc metal and metal-like carbide phases are revisited with special attention given to Tc-rich phases in the view of prospective nuclear fuel utilization and alternative transmutation targets fabrication. A new Tc-metal phase has been found and new softer conditions for the Tc carbide formation were observed. The unit cell parameters of a new orthorhombic Tc metal were a = 2.805(4), b = 4.958(8), c = 4.474(5)•ð (V/z = 15.55 •ð) for Tc-C with 1.38 wt.% C and a = 2.815(4), b = 4.963(8), c = 4.482(5) •ð (V/z = 15.65 A) for Tc-C with 1.96 wt.% C.
Attenuated total reflection-Fourier transform-infrared spectroscopy (ATR-FT-IR) analysis of 100 adhesive samples from different prehistoric composite artefacts, pottery, and amorphous lumps across Eastern Europe and Urals were conducted with the aim to establish a fast analytical screening method for adhesive assignment. The ATR-FT-IR analysis allowed the identification of major chemical components of the adhesive samples that were assigned to three main groups: birch bark tar without major additives, birch bark tar with additives, and minor/non-birch bark tar samples. ATR-FT-IR spectra were further analyzed using
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