An Autonomous Reference Frame for Relativistic GNSS

Current GNSS systems rely on global reference frames which are fixed to the Earth (via the ground stations) so their precision and stability in time are limited by our knowledge of the Earth dynamics. These drawbacks could be avoided by giving to the constellation of satellites the possibility of constituting by itself a primary and autonomous positioning system, without any a priori realization of a terrestrial reference frame. Our work shows that it is possible to construct such a system, an Autonomous Basis of Coordinates, via emission coordinates. Here we present the idea of the Autonomous Basis of Coordinates and its implementation in the perturbed space-time of Earth, where the motion of satellites, light propagation, and gravitational perturbations are treated in the formalism of general relativity.Comment: 5 pages, 3 figures, in proceedings of the 4th International Colloquium: Scientific and Fundamental Aspects of the Galileo Programme, 4-6 December 2013, Prague, Czech Republic; removed unnecessary indices from eqs. 3,6,7 and corrected minus signs in eqs. 6 and

Optics in the Schwarzschild space-time

Realistic modelling of radiation transfer in and from variable accretion disks around black holes requires the solution of the problem: find the constants of motion and equation of motion of a light-like geodesic connecting two arbitrary points in space. Here we give the complete solution of this problem in the Schwarzschild space-time.Comment: 14 pages, 10 figures, type C orbits added, analytic solutions for time of flight of photons for all 3 types of orbits adde

Phytochemical Analysis and Total Antioxidant Capacity of Rhizome, Above-Ground Vegetative Parts and Flower of Three Iris Species

This study was aimed at investigating the phytochemical composition and antioxidant capacity of rhizomes, above-ground vegetative parts and flowers of three Iris species: Iris humilis Georgi, Iris pumila L. and Iris variegata L. UHPLC-Orbitrap MS analysis was used for determination of phytochemical profile. Total pigments, phenolics, flavonoids, soluble sugars and starch content as well as ABTS antioxidant capacity were also determined. In total, 52 phenolics compounds were identified with 9 compounds (derivatives of iriflophenone, apigenin C-glycosides, luteolin O-glycoside, isoflavones derivatives of iristectorigenin, dichotomitin, nigracin and irilone) never reported before in Iris spp. Differences in phenolic composition profile, pigments, soluble sugar, starch, total phenolics and flavonoids content and total antioxidant capacity were found among Iris species and different part of plants. Significant correlation between total phenolic content and antioxidant capacity was determined. The obtained results are comparable with those obtained for medical plants. These findings could be useful for fingerprinting characterization of Iris species and estimation of possible use in pharmaceutical industries

Analytical time-like geodesics

Time-like orbits in Schwarzschild space-time are presented and classified in a very transparent and straightforward way into four types. The analytical solutions to orbit, time, and proper time equations are given for all orbit types in the form r=r(\lambda), t=t(\chi), and \tau=\tau(\chi), where \lambda\ is the true anomaly and \chi\ is a parameter along the orbit. A very simple relation between \lambda\ and \chi\ is also shown. These solutions are very useful for modeling temporal evolution of transient phenomena near black holes since they are expressed with Jacobi elliptic functions and elliptic integrals, which can be calculated very efficiently and accurately.Comment: 15 pages, 10 figures, accepted by General Relativity and Gravitatio

CHEMICAL COMPOSITION AND QUORUM SENSING INHIBITION ACTIVITY OF HORSERADISH (ARMORACIA RUSTICANA) ROOT EXTRACTS

During the past decades several quorum sensing inhibitors (QSI) of plant origin have been isolated and chemically characterized. QSI agents of plant origin represent potential alternative or complementary approach to antibiotic treatment of multidrug-resistant bacteria and infections caused by bacterial biofilms. The aim of the current study was to screen QSI activities of horseradish root extracts obtained using different organic solvents and different root processing methods (drying at 40°C, 60°C or extraction of fresh material). Common opportunistic pathogen Pseudomonas aeruginosa MMA83 was used for QSI screen. RT-qPCR was used to analyze the effect of the extract on the relative mRNA levels of the genes QS (lasR, lasI, rhlR, rhlI, mvfR, pqsH) and the genes involved in P. aeruginosa MMA83 virulence (lasB, phzM, rhlC, algK, pvdS). Chemical composition of extracts was determined by UHPLC Q-ToF MS analysis. The most active extract obtained using fresh roots and hexane/ethyl acetate (1:1) solvent mixture was able to significantly reduce content all examined mRNA. Qualitative chemical analysis reviled presence of 15 phenolic acids and their derivatives, 9 flavonoids and 10 glucosinolates in majority of examined extracts. It is significant to emphasize that the most active QSI extract did not contain a single one, out of ten dominant glucosinolates, which have undergone to hydrolysis yielding isothiocyanates and other sulphur-containing compounds responsible for QSI effects. Our results strongly indicate that even mild thermal treatment (40°C) of horseradish roots prior to extraction could lead to severe reduction or loss of QSI activity.Book of abstract: From biotechnology to human and planetary health XIII congress of microbiologists of Serbia with international participation Mikromed regio 5, ums series 24: 4th – 6th april 2024, Mona Plaza hotel, Belgrade, Serbi

Biocompounds from mushroom aqueous and polysaccharide extracts

The application of mushrooms for medicinal purposes has a long history, primarily due to its therapeutic properties. Today, mushrooms are often used as functional food or natural sources in the development of various nutraceuticals. Using advanced instrumental techniques, it was shown that mushrooms are a good source of highly valuable polysaccharides (i.e., glucans), sterols (i.e., ergosterol), different antioxidants, proteins and peptides. However, due to the great diversity of fungi, additional research in this area should be performed. The aim of this study is to analyze biocompounds from polysaccharides and aqueous extracts of two different mushrooms (A. bisporus and A. aegerita). Mushroom extracts were prepared according to procedure previously desribed by Popović Minić (2023)[1]. Lyophilised mushroom powder was extracted with 80% methanol containing 0.1% HCl, after which the suspension was filtered through 0.45μm filters and used for further chromatographic analysis by UHPLC-QToF-MS. Chemical characterization of mushroom biomolecules was performed using exact mass (m/z) and MS2 fragment ions of each detected compound and their retention times. The identified compounds represented four structurally distinct groups: 1) organic acids and their derivatives (7 compounds); 2) phenolic acids and their derivatives (11 compounds); 3) esters (28 compounds); and 4) other organic compounds (Gibberellin A1 ). Based on the obtained results, the differences between the tested samples can be clearly observed. In A.bisposrus and A.aegerita polysaccharide extracts only few organic acids and esters were detected, while phenolics and majority of esters were not recorded. On the other hand, the presence of organic acids, phenolic acids, esters and their derivatives was confirmed in both aqueous extracts. The highest number of detected compounds (as many as 41 compounds) was detected in the aqueous extract of A. aegerita. Among organic acids, fumaric, malic and citric acids were detected in all the mushroom extracts, whereas p-hydroxybenzoic acid, m-hydroxy-hydrocinnamic acid, sinapic acid, 2-(pentanoyloxy)benzoate, and 3-(11-hydroxyundecoxy) benzoate were detected among phenolic acids and their derivatives in aqueous extracts of both mushrooms. Regarding detected esters, following compounds were identified in the tested samples: 8-carboxyoctanoate, 3-(octyloxy)-3-oxopropanoate, 9,12,13-trihydroxyoctadecenoate, 13-hydroxy-9,11-octadecadienoate. The estimated profiles of biocompounds present in mushroom extracts can contribute to the further understanding of their antioxidant and biological properties

In vitro digestion of meat- and cereal-based food matrix enriched with grape extracts: How are polyphenol composition, bioaccessibility and antioxidant activity affected?

The aim of this study was to evaluate the effect of enriching a complex food matrix (FM) with grape extracts on polyphenol content, composition, bioaccessibility and antioxidant activity during digestion. The grape extracts and FM were separately tested under the same conditions as controls. The FM by itself contains a significant amount of phenolic acids and flavonols, influencing the final recovery of polyphenols from grape extracts. The FM significantly increased the total recovery of polyphenols after digestion of grape seed extracts compared to those digested without the FM; however, a low recovery of proantocyanidins and total flavonoids was observed. Digestive fluids and FM compounds significantly increased the total polyphenol content of grape digests and significantly contributed to their ABTS(center dot+) scavenging activity and ferrous-ion-chelating capacity. The present study suggested that enrichment of meat-and cereal-based products with grape polyphenol extracts could be a good strategy to formulate a healthier diet

Data security in mobile healthcare

Introduction/purpose: The digitization of healthcare has gained particular importance in the years since the emergence of COVID-19 and also has become one of the primary goals of the Government of the Republic of Serbia. Telemedicine is a good solution when the patient cannot come to a healthcare facility. Mobile healthcare applications are already widely used, but in both fields the important challenge is data security. The aim of this paper is to review solutions for data security in mobile healthcare from the technical side and possible challenges in the process of digitization of the healthcare system in Serbia. Methods: This review is based on current papers in this area, on the available relevant literature and the authors' many years of experience in this field. Experiences in the process of digitization of healthcare in Serbia are based on available articles and regulations. Finally, possible challenges are presented from the authors' perspective based on everything presented in the field of data security in mobile healthcare. Results: The analysis of the papers reviewed from the point of view of data security showed that users are often ready to sacrifice their privacy for the sake of convenience provided by mobile applications. Conclusion: Based on the review of the papers and clear data security requirements that include the presented safeguards, one of the main tasks of the entire community is to raise awareness of information security and awareness of the need for cyber hygiene of each individual, which is the basis for the safe use of e-health services

Polyphenolic Profile, Antioxidant and Antidiabetic Potential of Medlar (Mespilus germanica L.), Blackthorn (Prunus spinosa L.) and Common Hawthorn (Crataegus monogyna Jacq.) Fruit Extracts from Serbia

Plant-based food represents an excellent source of different nutrients and bioactive compounds, such as phenolics, carotenoids, vitamins, etc., with proven health benefits for humans. The content of selected phytochemicals, polyphenolic profile, and biological activity (antioxidant potential and α-glucosidase inhibitory activity) of fruit extracts of medlar (Mespilus germanica L.), blackthorn (Prunus spinosa L.), and common hawthorn (Crataegus monogyna Jacq.), the neglected Rosaceae species originated from Serbia were studied. Targeted UHPLC/(−)HESI–MS/MS quantitative analysis of phenolic compounds revealed pinocembrin only in medlar fruit extract, and it is the first report of this flavanone in medlar fruits. Total phenolic content did not differ between extracts, whereas significant differences were observed for the contents of total flavonoids, total phenolic acids, and total gallotannins. Monomeric anthocyanins and total anthocyanins were significantly higher in blackthorn compared to medlar and hawthorn fruit extracts (p < 0.05). DPPH· and ABTS·+ scavenging activities for examined fruits were modest compared to other natural antioxidants and BHT. The most potent inhibitory activity toward α-glucosidase expressed medlar and blackthorn extracts with IC50 values of 129.46 and 199.84 μg/mL, respectively, which was higher compared to the standard drug acarbose