Poly(vinyl alcohol)/heteropolyacid nanocomposites as new materials for radiochromic dosimetry in radiation processing

Radiochromic films composed of polymer matrices and organic dyes are widely used for routine dosimetry purposes in operation of various radiation facilities—gamma and X-ray-irradiation, electron accelerators, and so on. However, the sensitivity of these films rapidly decreases at doses exceeding 30–50 kGy due to a saturation of their optical response, making them unsuitable for accurate dosimetry in radiation processing of polymers and composites where doses up to 200 kGy are typically employed. To overcome this limitation, the use of inorganic substances as the coloring agents of polymer-based radiochromic films was proposed in this paper, specifically, heteropolyacidacid H₃PW₁₂O₄₀ (tungstophosphoric acid) in the matrix of poly(vinyl alcohol) (PVA). Nanocomposite PVA/H₃PW₁₂O₄₀ films were prepared by solution casting and their optical responses toward ⁶⁰Co gamma radiation and beams of 6 MeV electrons for a dose range of 10–200 kGy were investigated. It was established that upon exposure to gamma rays and electron beams, the films turn blue and a broad absorption band at 750 nm appears in their spectra. Importantly, the radiation-induced optical absorption increases in a linear fashion up to the dose of 150 kGy and only slightly deviates from linearity at 200 kGy. Moreover, it was found that the PVA/H₃PW₁₂O₄₀ films have a long shelf life, are dose-rate independent within a wide range, and color-stable after irradiation. All these features make the nanocomposite PVA/H₃PW₁₂O₄₀ films promising for use as routine dosimeters and dose labels in a much wider range of high doses as compared to radiochromic films based on organic dyes.     

Order parameter of side groups of a polysiloxane in liquid crystalline uniaxial phases

The orientational order of a liquid crystalline side chain polysiloxane has been investigated by means of polarized light spectroscopy and dielectric relaxation measurements. The order parameters (P₂) and (P₄) have been determined as a function of the temperature for the smectic and nematic phases. The orienting properties of the polysiloxane investigated have been compared with those of a polysiloxane with the same mesogenic groups, but a shorter spacer.     

Study of orientational order in a nematic polysiloxane by utilizing the “guest–host” effect

A nematogenic side-chain polysiloxane is investigated by means of absorption and fluo-rescence spectroscopy.4-Dimethylamino-4′-nitrostilbene (DANS) is dissolved in the poly-meric matrix as a guest probe. The orientational order and the molecular distribution function have been determined from measurements of polarized absorption and fluorescence spectra. It has been found that fluorescence spectroscopy affords a method for determination of the phase transition temperatures of liquid–crystalline polymers. © 1993 John Wiley & Sons, Inc.     

Analysis of nanopore arrangement and structural features of anodic alumina layers formed by two-step anodizing in oxalic acid using the dedicated executable software

Anodic porous alumina layers were fabricated by a two-step self-organized anodization in 0.3 M oxalic acid under various anodizing potentials ranging from 30 to 60 V at two different temperatures (10 and 17 ^°C). The effect of anodizing conditions on structural features and pore arrangement of AAO was investigated in detail by using the dedicated executable publication combined with ImageJ software. With increasing anodizing potential, a linear increase of the average pore diameter, interpore distance, wall thickness and barrier layer thickness, as well as a decrease of the pore density, were observed. In addition, the higher pore diameter and porosity values were obtained for samples anodized at the elevated temperature, independently of the anodizing potential. A degree of pore order was investigated on the basis of Delaunay triangulations (defect maps) and calculation of pair distribution or angle distribution functions (PDF or ADF), respectively. All methods confirmed that in order to obtain nanoporous alumina with the best, hexagonal pore arrangement, the potential of 40 V should be applied during anodization. It was confirmed that the dedicated executable publication can be used to a fast and complex analysis of nanopore arrangement and structural features of nanoporous oxide layers.     

Ramsey’s theorem for colors from a metric space

The Ramsey theorem says that for any countably infinite undirected clique whose edges are colored by a finite number of colors, there is an infinite subclique whose edges are colored by a single color. In this note, we generalize the theorem to a situation where the colors form a compact metric space.     

Superposition solutions to the extended KdV equation for water surface waves

Nonlinear Dynamics - The KdV equation can be derived in the shallow water limit of the Euler equations. Over the last few decades, this equation has been extended to include higher-order effects....     

Self‐Referencing Background Correction Method for Voltammetric Investigation of Reversible Redox Reaction

This paper presents a novel fully automated background correction method, which internally validates its results. The method requires a set of voltammograms recorded for calibration with different sensitivities but offers reproducibility, high precision and accuracy. In this paper the results obtained with the use of the proposed algorithm were verified by the processing of both simulated and experimentally registered signals. In both cases recovery and confidence intervals were very satisfactory.     

Normalization in MALDI-TOF imaging datasets of proteins: practical considerations

Normalization is critically important for the proper interpretation of matrix-assisted laser desorption/ionization (MALDI) imaging datasets. The effects of the commonly used normalization techniques based on total ion count (TIC) or vector norm normalization are significant, and they are frequently beneficial. In certain cases, however, these normalization algorithms may produce misleading results and possibly lead to wrong conclusions, e.g. regarding to potential biomarker distributions. This is typical for tissues in which signals of prominent abundance are present in confined areas, such as insulin in the pancreas or β-amyloid peptides in the brain. In this work, we investigated whether normalization can be improved if dominant signals are excluded from the calculation. Because manual interaction with the data (e.g., defining the abundant signals) is not desired for routine analysis, we investigated two alternatives: normalization on the spectra noise level or on the median of signal intensities in the spectrum. Normalization on the median and the noise level was found to be significantly more robust against artifact generation compared to normalization on the TIC. Therefore, we propose to include these normalization methods in the standard “toolbox” of MALDI imaging for reliable results under conditions of automation.