New relationship of displacement signal at quadrant photodiode: Control signal analysis and simulation of a laser tracker

New relationship of displacement signal using opposite sectors on a quadrant photodiode is derived. Standard and new displacement signals are analyzed in details. Through MATLAB^® laser tracking simulation models, based on common and suggested approaches, detailed analysis is performed, and it is shown that better results for the new relationship signal processing are obtained. Within new relationship of displacement signal, the sensitivity of the system to the displacement of the spot increases and, hence, provides better accuracy in positioning up to 30%.     

Physicochemical investigation of some archaeometallurgical findings from locality Kmpije (Bor,Serbia)

Preliminary results of physicochemical investigation of some archaeometallurgical findings from Kmpije locality in vicinity of Bor (Serbia) are presented in this paper. Ancient samples of prehistoric origin were investigated using different instrumental analytic methods—chemical, differential thermal, X-ray diffraction, and energy dispersive X-ray fluorescence analysis. Obtained results indicate to the presence of ancient metallurgical activities, so locality Kmpije may be considered as an archaeometallurgical site, which should be investigated more in future for more precise details.     

EDXRF spectrometry determination of tungsten in tobacco plants after antiviral treatment with 12-tungstophosphoric acid and its compounds

In this study, we have developed a sensitive, rapid and simple procedure for the energy dispersive X-ray fluorescence (EDXRF) spectrometry measurement of tungsten in tobacco plant parts. Only 0.1 g of dried plant material is needed instead of the usual 1 g. EDXRF spectrometry is used for quantitative measurement, after the foliar application of solutions of tungstophosphoric acid (WPA), its magnesium salt and compounds with glycine (Gly) and alanine (Ala), in exact quantities. After that, the leaves, trunks and summits were collected and prepared separately. Tungsten is determined directly in raw dried material, and the overlap of the tungsten peak with zinc's that is present is avoided by the spectral deconvolution to obtain quantitative results. The prepared dry tablets weighed 100 mg, and measurement time was 2000 s. The radioisotope excitation source used was ¹⁰⁹Cd and tungsten was identified and quantified at the L_α1 and L_α2 lines at the energies of 8397.6 eV and 8335.2 eV, respectively. EDXRF spectrometry was applied in a wide range of concentrations (up to 2000 mg/kg), with an estimated detection concentration limit of 15 mg/kg, calculated on dried material. Quantitative analysis of different parts of the treated plant plus the washings gave 94.47% recovery of the applied tungsten in different compound forms. After the foliar application of investigated WPA compounds, there were noticed both vertical and horizontal distributions of tungsten through out the tobacco plants, according to the EDXRF spectrometry results. This conclusion is also in agreement with the positive effects of WPA on Tobacco mosaic tobamovirus (TMV) infection of Nicotiana tabacum (Solanaceae).     

Microbial Natural Products with Antiviral Activities,Including Anti-SARS-CoV-2: A Review

The SARS-CoV-2 virus, which caused the COVID-19 infection, was discovered two and a half years ago. It caused a global pandemic, resulting in millions of deaths and substantial damage to the worldwide economy. Currently, only a few vaccines and antiviral drugs are available to combat SARS-CoV-2. However, there has been an increase in virus-related research, including exploring new drugs and their repurposing. Since discovering penicillin, natural products, particularly those derived from microbes, have been viewed as an abundant source of lead compounds for drug discovery. These compounds treat bacterial, fungal, parasitic, and viral infections. This review incorporates evidence from the available research publications on isolated and identified natural products derived from microbes with anti-hepatitis, anti-herpes simplex, anti-HIV, anti-influenza, anti-respiratory syncytial virus, and anti-SARS-CoV-2 properties. About 131 compounds with in vitro antiviral activity and 1 compound with both in vitro and in vivo activity have been isolated from microorganisms, and the mechanism of action for some of these compounds has been described. Recent reports have shown that natural products produced by the microbes, such as aurasperone A, neochinulin A and B, and aspulvinone D, M, and R, have potent in vitro anti-SARS-CoV-2 activity, targeting the main protease (M^pro). In the near and distant future, these molecules could be used to develop antiviral drugs for treating infections and preventing the spread of disease.     

Recent trends in image evaluation of HPTLC chromatograms

Abstract

In the current article, an overview of recent applications and opportunities of image evaluation of high-performance thin-layer chromatograms (HPTLC) in food analysis and natural product research is presented. The article shortly covers the aspects of specialized software packages for image analysis, image post-correction, signal acquisition, and preprocessing. Contemporary aspects of image-based HPTLC fingerprinting, quantification of target compounds, and advanced chemometric modeling were reviewed. Special attention was dedicated to freely available software packages. Advantages and disadvantages of each one were discussed in terms of abilities to obtain chromatographic profiles and perform crucial steps in signal manipulation, such as background subtraction, denoising, and background detrending. The most frequently applied techniques for signal manipulation have been discussed and recommendation provided. In that sense, the article aims to provide a valuable guideline for readers dealing with the application of HPTLC image analysis in food and natural products research, especially in connection with the most frequently used chemometric techniques, in domains of pattern recognition, classification, and regression.     

Preparation and characterization of PLA composites with modified magnesium hydroxide obtained from seawater

Journal of Thermal Analysis and Calorimetry - Modification of poly(lactic acid) (PLA) was performed with the surface modified magnesium hydroxide (mMH) obtained from seawater. Surface modification...     

Characterization of poly(ethylene oxide) modified with different phenyl hepta isobutyl polyhedral oligomeric silsesquioxanes

Journal of Thermal Analysis and Calorimetry - Poly(ethylene oxide)/polyhedral oligomeric silsesquioxanes (PEO/POSSs) composites were prepared by the melting method. The investigation of their...     

Thermal stability of poly(methyl methacrylate)/silica nano- and microcomposites as investigated by dynamic-mechanical experiments

The thermal stability of poly(methyl methacrylate) (PMMA) filled with silicon dioxide particles was investigated by means of rheological tests. The change in the storage modulus G′ was measured, which is a very sensitive method to detect molecular changes in polymers. The long-term thermal stability of the composites was found to depend on the temperature of the melt, the size of the silica particles, which ranged from nano- to micrometers, and the volume fraction of the filler. For high temperatures and a large surface area of the silica particles the behaviour of the composites differs significantly from that of the pure polymer. Pure PMMA degrades at high temperatures, which correlates with a decrease of G′. In contrast an increase in G′ with increasing temperature and filler surface was measured for the composite materials. This behaviour is explained by chemical reactions of the PMMA molecules with the silica particles. Effects of that kind were not found for SiO₂ filled polystyrene.