SCIDAR - Дигитална архива Универзитета у Крагујевцу
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The research of the influence of traverse speed and depth of cut on surface roughness in abrasive water jet machining
Full text linkThe main goal in today's production is to make as many products as possible in the shortest possible time. When machining with an abrasive water jet, this means that it is necessary to cut with the highest possible traverse speeds. Machining with a high traverse speed results in an increase in the surface roughness parameters of the surface machined with an abrasive water jet. With the increase in the thickness of the machined material, i.e. the depth of the cut, this is more and more pronounced. The aim of this work is to determine the influence of traverse speed on the roughness of the machined surface, Ra. Also, the influence of the thickness of the samples on the roughness of the processed surface, Ra, was investigated. The material of the samples was AlMg3 of different thicknesses (6, 8, 10 and 12 mm). The samples were cut with traverse speed of 200, 400, 600, 800, 1000 and 1200 mm/min. The roughness parameter of the machined surface, Ra, was measured at different depths, h and at several places along the samples. Based on the measured values of Ra, it was concluded that with the increase in traverse speed, the roughness of the machined surface increases. It was observed that the roughness parameter Ra at the same depth of measurement, h, has approximately the same values. The mathematical model, that describes the influence of traverse speed on the roughness of the machined surface was developed. This model showed satisfactory agreement with the measured values.Publishe
EFFECTS OF STANDARDIZED ARONIA MELANOCARPA EXTRACT ON CARDIOVASCULAR SYSTEM: FROM BASIC TO APPLIED INVESTIGATION
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BIOCHEMICAL RESEARCH OF THE SPECIES ORCHIS MORIO L. FROM ZLATAR
Full text linkSalep tuber is sourced from young tubers of plants belonging to genera such as Orchis (Orchis morio L, Orchis militaris L, Orchis mascula L, Orchis latifolia L), Ophrys (Ophrys fuciflora (Cr) Haller), Platanthera (Platanthera bifolia (L) Rich,), Anacamptis (Anacamptis pyramidalis (L) Rich), and Gymnadenia (Gymnadenia conopsea (L) RBr) from the Orchidaceae family. Ph.Yug.II categorizes Orchis morio L as salep, aligning with CITES convention and IUCN categories for vulnerable species. As a mucilaginous drug, salep is used as an enema for intestinal catarrh and added to drugs with local irritating effects due to its soothing impact on mucous membranes. Qualitative gas chromatographic-mass spectrometric (GH/MS) analysis of Orchis morio tubers from Zlatar mountain’s dry meadows reveals compounds like cinnamaldehyde, α-terpinyl acetate, coumarin, α-muurolol, pogostol, caryophyllene, n-hexadecanoic acid, linoleic acid, pentacosane, heptacosane, nonacosane, campesterol, cyclolartenol, sitosterol, and predominantly β-sitosterol. The elevated β-sitosterol content supports the use of salep in treating benign prostate diseases.Publishe
Anti-disturbance state estimation for PDT-switched RDNNs utilizing time-sampling and space-splitting measurements
No full textAnti-disturbance state estimation for reaction–diffusion neural networks (RDNNs) subject to persistent dwell-time (PDT) switching constraints is investigated in this paper. First, PDT switching that can be utilized to characterize both the fast and slow switching processes is used in this paper to accurately model the RDNNs. Moreover, by designing the time-sampling and space-splitting measurement algorithms, the proposed state estimator can significantly reduce the measurement cost while tolerating the frequent asynchrony of the system modes and estimator ones caused by the sensor update lag. Furthermore, a state estimator is constructed to obtain the state of RDNNs affected by matched disturbances. To suppress the impact of the
disturbance on the system’s state estimation, a disturbance observer and a disturbance-related controller are designed to estimate the disturbance information and ensure state estimation performance. Then, sufficient conditions for the proposed state estimator making the estimation error bounded are derived. Finally, numerical simulations for switched RDNNs with twodimensional spatial diffusion are presented to illustrate the effectiveness and superiority of the proposed method.Publishe
Biosynthesis and characterization of silver nanoparticles synthesized using extracts of Agrimonia eupatoria L. and in vitro and in vivo studies of potential medicinal applications
No full textThis research explores the synthesis, characterization, and biological activities of silver nanoparticles (AgNPs) derived from acetone (AgNPs-acetone) and aqueous (AgNPs-H2O) extracts of Agrimonia eupatoria. The nanoparticles exhibit isometric morphology and uniform size distribution, as elucidated through Transmission Electron Microscopy (TEM) and high-resolution TEM (HRTEM) analyses. The utilization of Scanning Transmission Microscopy (STEM) with High-Angle Annular Dark-Field (HAADF) imaging and energy dispersive spectrometry (EDS) confirms the crystalline nature of AgNPs. Fourier Transform Infrared (FTIR) analysis reveals identical functional groups in the plant extracts and their corresponding AgNPs, suggesting the involvement of phytochemicals in the reduction of silver ions. Spectrophotometric monitoring of the synthesis process, influenced by various parameters, provides insights into the kinetics and optimal conditions for AgNP formation. The antioxidant activities of the plant extracts and synthesized AgNPs are evaluated through DPPH and ABTS methods, highlighting AgNPs-acetone as a potent antioxidant. Third-instar larvae exposed to the extracts have differential effects on DNA damage, with the acetone extract demonstrating antigenotoxic properties. Similarly, biosynthesized AgNPs-acetone displays antigenotoxic effects against EMS-induced DNA damage. The genotoxic effect of water extract and AgNPs-acetone was dose-dependent. Hemolytic potential is assessed on rat erythrocytes, revealing that low concentrations of AgNPs-acetone and AgNPs-H2O had a nontoxic effect on erythrocytes. Cytotoxicity assays demonstrate time-dependent and dose-dependent effects, with AgNPs-acetone exhibiting superior cytotoxicity. Proapoptotic activity is confirmed through apoptosis induction, emphasizing the potential therapeutic applications of AgNPs. The antimicrobial activity of AgNPs reveals concentration-dependent effects. AgNPs-H2O display better antibacterial activity, while antifungal activities are comparable between the two nanoparticle types.Publishe
The Assessment of Sewage Sludge Utilization in Closed-Loop Economy from an Environmental Perspective
Full text linkSewage sludge, a by-product of wastewater treatment, is garnering increasing attention in the pursuit of closed-loop economy practices due to its highly beneficial fertilizing properties. However, like any technique, using sewage sludge as fertilizer has potential and limitations. Heavy metals within sewage sludge are a primary limitation curtailing its application as a fertilizer. This study collected sewage sludge samples from four wastewater treatment plants and soil from potential application sites. The mobility of heavy metals was then examined using a sequential BCR analysis. Furthermore, a comprehensive environmental risk assessment associated with the agricultural use of sewage sludge was conducted, using various risk indicators such as Igeo and Nemerov, to compare the cumulative metal concentrations in the sewage sludge and soil. Additionally, risk assessment, ecological risk indices of metal mobility, and environmental risk indices were calculated, specifically focusing on the mobility of metals in the soil environment. This research demonstrates that sewage sludge failing to meet conventional criteria for agricultural use based on total metal content does not necessarily pose a high-risk application. Understanding the mobility forms of metals in sewage sludge is crucial, influencing the analysis of their potential utilization. Importantly, sewage sludge from wastewater treatment plants utilizing biological bed technology tends to exhibit a higher tendency of heavy metals to exist in mobile forms, migrating within the soil environment.Publishe
THE INFLUENCE OF SATURATED SOLUTIONS OF MINERAL SALTS ON SAPROPHITIC BACTERIA IN THE SOIL
Full text linkThe paper provides an overview of the influence of saturated salt solutions on the number and structure of bacterial complexes in soil, as well as pure cultures of bacteria isolated from that soil. The short-term action of high doses of salt is not fatal for saprophytic bacteria in the soil. Nitrogen salts exert the greatest influence on the mentioned parameters, especially ammonium nitrate. Bacilli and sliding bacteria are the most resistant to the effects of salt.Publishe
FIRE AS A CREATIVE PRINCIPLE IN THE SECONDARY SKY BY VASKO POPA
No full textThe poetic cosmogony of Vasko Popa translated into a collection entitled Secondary Sky was designed on a specific space-time plan, the coordinates of which can be read within the seven poetic cycles of the aforementioned collection. By devising a side sky, Popa represents a creative principle that is announced within the collection, and one of the ways of manifesting these principles is represented by the symbol of
fire. The equivalent of cosmic creation is an alchemical creation, so in that sense one should especially focus on fire as a symbol of creative stimulation. The goal of the paper is to shed light on the connection of the solar principle within Popa’s Secondary Sky with the creative principle, in order to reveal the multiple functions and symbolism of fire (from the point of view of myth and folklore). Fire manifests itself in Secondary
Sky through numerous modifications of the primary motif: as a hearth, living fire, smoke, ashes and sun. Bearing in mind such a wide range of forms of manifestation of the symbol of fire, the conducted research is mainly directed towards monitoring the development and transformations of its meanings within the poetic collectionPublishe
ASSESSMENT OF GALIUM VERUM EXTRACT SUPPLEMENTATION ON REDOX HOMEOSTASIS IN PSORIATIC RAT MODEL
Full text linkPsoriasis lacks comprehensive data on its systemic oxidative impact. This study explores Galium verum extract’s influence on systemic oxidative state in psoriatic rats. Twenty-four male W.albino rats were divided into control (CTRL), psoriasis (PSORI) and psoriasis treated with G.verum extract (PSORI+GV) groups. Blood samples analyzed for redox state biomarkers revealed increased TBARS levels in PSORI vs CTRL and PSORI+GV. PSORI exhibited significantly lower nitrite levels compared to CTRL and PSORI+GV, with elevated O2- and H2O2 levels. GSH and SOD values were reduced in PSORI and PSORI+GV, while catalase activity increased. G.verum extract positively modulated psoriatic rat redox state.Publishe
ENHANCING THE EXTRACTION EFFICIENCY OF CAFTARIC ACID FROM GRAPE PULP THROUGHT OPTIMIZATION PROCESS
Full text linkThis study explores the impact of operational extraction parameters, including ethanol concentration, extraction time, and temperature, on the extraction of caftaric acid from grape pulp. Optimal conditions for maximizing caftaric acid content were identified as follows: 20% ethanol concentration, 300 minutes extraction time, and a temperature of 35°C. The investigation employed a full factorial experimental plan (23) to assess the influence of these operational factors on caftaric acid contents.Publishe