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Mechanical Properties of Repaired Welded Pipe Joints Made of Heat-Resistant Steel P92
No full textThis research provides a detailed investigation into the mechanical properties and microstructural evolution of heat-resistant steel P92 subjected to both initial (i) welding procedures and simulated (ii) repair welding. The study addresses the influence of critical welding parameters, including preheating temperature, heat input, and post-weld heat treatment (PWHT), with a particular emphasis on the metallurgical consequences arising from the application of repair welding thermal cycles. Through the analysis of three welding probes—initially welded pipes using the PF (vertical upwards) and PC (horizontal–vertical) welding positions, and a PF-welded pipe undergoing a simulated repair welding (also in the PF position)—the research compares microstructure in the parent material (PM), weld metal (WM), and heat-affected zone (HAZ). Recognizing the practical limitations and challenges associated with achieving complete removal of the original WM under the limited (in-field) repair welding, this study provides a comprehensive comparative analysis of uniaxial tensile properties, impact toughness evaluated via Charpy V-notch testing, and microhardness measurements conducted at room temperature. Furthermore, the research critically analyzes the influence of the complex thermal cycles experienced during both the initial welding and repair welding procedures to elucidate the practical application limits of this high-alloyed, heat-resistant P92 steel in demanding service conditions
Screening for polysaccharide producers among four different natural isolates of fungi
No full textIntroduction: The traditional medicine of many cultures uses mushrooms to
maintain and improve vitality and health. Their application as food is
spreading even more around the globe. Of the many biologically active
compounds present in them, the most abundant are polysaccharides,
terpenes, phenols, lectin, etc. Polysaccharides are complex carbohydrates
that play a key role in various biological processes. They are found in diverse
forms across the natural world, with higher fungi being a notable source. The
polysaccharides and mycelium biomass derived from these fungi have
attracted considerable interest due to their various applications in the food
and pharmaceutical sectors. Mycelial growth is greatly dependent on
fermentation media and physical conditions. The present study aims to test
the ability of four new isolates of higher fungi to produce intracellular (IPS)
and extracellular (EPS) polysaccharides during submerged fermentation
Spatial source-oriented analysis and probabilistic health risk assessment of potentially toxic elements in soils integrating the Geo-detector, APCS-MLR, and Monte-Carlo models
No full textSoil plays a crucial role in the ecological environment, and potentially toxic elements (PTEs) within the soil are a widespread concern due to their potential threat to environmental security and human health. This study applied multiple methods to analyze the potential sources and evaluate the human health risk of PTEs in 291 surface soil samples collected from Sichuan basin. The statistical results showed that the average contents of PTEs were 8.01 (As), 0.19 (Cd), 66.10 (Cr), 0.06 (Hg), 19.95 (Pb), 21.22 (Cu), 30.47 (Ni) and 66.53 (Zn) mg/kg, with Hg exhibited the highest variability. The geochemical baseline contents (GBCs) of PTEs were established through the cumulative frequency distribution curves, and the mean contents of PTEs were lower than their GBCs and background levels of Chengdu city. Four main sources of PTEs were identified by the Geo-detector and principal component analysis-absolute principal component score-multiple linear regression (PCA-APCS-MLR) model: natural process (35.37 %; Zn, Ni, Cd, and Cu), traffic source (28.78 %; Pb, Cr, and Ni), agricultural activities (14.81 %; As), and industrial emission and waste disposal (4.29 %; Hg). The results of the human health risk assessment (HHRA) model and Monte Carlo simulation revealed that both the non-carcinogenic and carcinogenic risk for children and adults was below the unacceptable limits (max of the THI and TCR for children: 0.8847, 2.44 ×10-5; adults: 0.1497, 2.00 ×10-5), and children faced a higher risk compared with adults (mean values of the THI and TCR for children: 0.2714, 6.92 ×10-6; adults: 0.0463, 5.64 ×10-6). Factor 3 (agricultural activities) contributed the most to health risks (44.2 %-64.05 %), and As was considered as the leading element contributing to health hazards, with ingestion (72.06 %-88.35 %) and dermal contact (40.39 %-66.55 %) as the primary exposure pathways for children and adults, respectively. These findings highlight the significance of incorporating spatial heterogeneity into the risk assessment of PTEs pollution, and also offer valuable cues for formulating region - specific policies to minimize the pollution hazards of soil PTEs
Quantitative Structure–Retention Relationship Approach in Assessing the Chloroacetamides’ Biological Profile
No full textChloroacetamides (CAAs) are an important class of synthetic herbicides long utilized in agriculture for their strong weed-control efficacy. However, their environmental and health impacts have raised significant concerns. Therefore, both the structural modification of known active compounds and the identification and design of new compounds with desirable properties and biological activity represent a significant challenge in pesticide chemistry. The bioactivity parameters of 18 new chloroacetamide derivatives were evaluated by using both in silico and chromatographic approaches. Correlation of chromatographic parameters with software-derived log P and EC50 values by linear regression analysis identified key structural factors affecting their lipophilicity and potential toxicity to non-target organisms. Multivariate analysis revealed and quantified that the total number of carbon atoms in the molecule (determines lipophilicity), along with the chemical nature of the hydrocarbon substituent (affects water solubility), plays a major role in shaping the biological profile of the tested derivatives. Moreover, it was found that the number of rotatable bonds significantly influences their toxicity. Furthermore, the results show that chromatographic parameter RM0 can serve as an alternative measure of lipophilicity, while the parameter m can indicate toxicity of the analyzed CCAs’
Mapping conformity assessment bodies in the Republic of Serbia: focus on ISO/IEC 17025 accredited laboratories
No full textThe contemporary development of the society is characterized by a rapid and intensive development of technology and industry, which leads to the appearance of an increasing amount of different products, but also to environmental pollution as product of their work. In everyday life, before placing products on the market, it is necessary to test them. These tests are conducted by testing laboratories in accordance with the relevant specifications for the given products. In case these tests are performed in laboratories accredited to ISO/IEC 17025:2017 ‘General requirements for the competence of testing and calibration laboratories’, by an accreditation body in a country that is a signatory to the ILAC Mutual Recognition Arrangement (ILAC MRA), their results will be recognized internationally. The basic goal of this paper is to present the current state of accredited laboratories in the Republic of Serbia, i.e., the analysis of the first accreditations granted, the distribution of laboratories by cities in Serbia, the number of testing methods in accredited laboratories, as well as the subject of testing/calibration in them. In addition, statistical multivariate analyses—Pearson’s correlation matrix and Principal Component Analysis—were performed to determine the correlation between accredited laboratories and socio-political parameters, as well as the similarity in the distribution of accredited organizations in Serbia. The results show that the Republic of Serbia has a fairly developed area of quality infrastructure, that there is a certain relation between the granting of initial accreditation and certain socio-political events, as well as that there is a linear dependence between the number of accredited testing and calibration laboratories and the socio-economic parameters of the city. In Serbia, the largest number of accredited testing laboratories analyze media from the environment, however, a large number of those that deal with the testing of materials, food and industrial equipment are also present
Self-compatibility in plum cultivars released from a breeding program in Serbia
No full textThe breeding program at the Fruit Research Institute, Čačak has released eighteen plum cultivars. Over two years, the self-compatibility of fifteen of these cultivars was determined, with open pollination used as a comparison. Pollen germination in vitro was tested in each cultivar. For observing pollen tube growth in vivo, self- and open pollinated pistils were fixed on the 3, 6 and 10 days after pollination or full flowering. Fixed samples were stained with fluorochromic stain aniline-blue and observed under the microscope. In both pollination treatments initial and final fruit set was determined. In six cultivars, average two-year pollen germination was above 31 %, while in the other cultivars it was below 27.0 %. In both years, pollen tube growth in the majority of cultivars finished after ten days (except ‘Jelica’, ‘Čačanska Rana’, ‘Čačanska Najbolja’, and ‘Čačanski Šećer’) with penetration into the nucellus. Pollen tube growth in both treatments was better in the Year 2, when the mean daily temperature was 5°C higher. The slower pollen tube growth of the abovementioned cultivars, except for ‘Jelica’, was followed by low initial fruit set. The highest rate of final set was found in ‘Krina’ and ‘Zlatka’ (36.9 % and 35.5 %), whereas in ‘Čačanska Rana’, ‘Čačanska Najbolja’ and ‘Čačanski Šećer’ no fruit were harvested. Plum cultivars developed at Čačak are self-compatible (‘Čačanska Lepotica’, ‘Čačanska Rodna’, ‘Valjevka’, ‘Valerija’, ‘Mildora’, ‘Boranka’, ‘Krina’, ‘Zlatka’, ‘Pozna Plava’) or partially self-compatible (‘Jelica’, ‘Timočanka’, ʻNada’), or self-incompatible (‘Čačanska Rana’, ‘Čačanska Najbolja’, ‘Čačanski Šećer’)
Standardization of photon correlation spectroscopy as a method for determining the size of immunocomplexes for diagnostic purposes
No full textУ овој докторској дисертацији испитана је применa фотон корелационеспектроскопије за одређивање величине колоидних честица имунокомплекса удијагностичке сврхе.Након потврде да је фотон корелационом спектроскопијом могуће анализиративеличину тј. хидродинамички пречник колоидних честица у in vitro формиранимимунокомплексима, овом методом је анализирана величина честица у циркулишућимимунокомплексима (CIC) 30 особа са реуматоидним артритисом (РА) и 30 здравих особа.И у контролним CIC узорцима и CIC узорцима особа са РА је на основу величинедетектовано 50 типова честица. За CIC узорке особа са РА је, у односу на контролу, билакарактеристична значајно већа заступљеност честица пречника 28,2, 531, 712 и 1718 nmи мања заступљеност честице пречника 78,8 nm. Промене у нивоу садржајаимуноглобулина у CIC узорцима особа са РА се нису подударале са обрасцем расподелевеличина детектованих честица. Значајно повећан ниво IgA у CIC узорцима особа са РАу поређењу са контролом је повезан са 28 типова честица. Значајно повишен нивоукупних IgG у CIC узорцима особа са РА је повезан са честицама пречника 7,5, 18,2,21,0, 24,0, 220, 396, 712, и 812 nm, а повећан ниво IgM је повезан са честицама пречника32,7, 43,8, 220, 396, 531 и 1281 nm. Истовремено повећање нивоа све три класеимуноглобулина у CIC узорцима особа са РА, у поређењу са контролом, показано je самоу CIC узорцима који садрже честице од 220 и 396 nm.Добијени резултати су показали да се фотон корелационом спектроскопијом можеодредити величина колоидних честица у CIC у физиолошким и патолошким стањима ити подаци би се, након потврде у студијама већег обима, могли користити за дијагнозу,праћење прогресије болести и тестирање ефикасности терапијских протокола болести учију патогенезу су укључени имунокомплекси.This doctoral dissertation investigates the application of photon correlationspectroscopy (PCS) for determining the size of colloidal particles in immune complexes indiagnostic.After validating PCS as a method for analyzing the hydrodynamic diameter of theparticles in vitro-formed immune complexes, it was applied to study the particle size incirculating immune complexes (CICs) from 30 individuals with rheumatoid arthritis (RA) and30 healthy controls. In both control and RA CIC samples, 50 distinct particle size types wereidentified. Notably, CICs from individuals with RA exhibited a significantly higher prevalenceof particles with diameters of 28,2, 531, 712, and 1718 nm, and a lower prevalence of particleswith a diameter of 78,8 nm, compared to controls. This particle distribution pattern did notreflect the changes in the CIC immunoglobulin level. A marked increase in IgA levels in RACIC samples was associated with 28 particle types. Furthermore, elevated total IgG levels inRA CIC samples were linked to particles with diameters of 7,5, 18,2, 21, 24, 220, 396, 712, and812 nm, while increased IgM levels corresponded to particles with diameters of 32,7, 43,8, 220,396, 531, and 1281 nm. Concurrent elevations in all three immunoglobulin classes wereobserved only in CIC samples containing particles of 220 and 396 nm.These findings demonstrate that PCS is capable of accurately determining the sizedistribution of colloidal particles in CICs under both physiological and pathological conditions.With further validation in larger studies, this method could be employed for diagnosticpurposes, monitoring disease progression, and evaluating the effectiveness of therapeuticinterventions in diseases where immune complexes play a key role in pathogenesis
Novel multiphase composite electrode decorated with Pd nanoparticles for electrochemical determination of herbicides
No full textThis study investigates the electrochemical determination of dicamba (3,6-dichloro-2-methoxybenzoic acid, DIC) and 2,4-D-dichlorophenoxyacetic acid (2,4-D) using a palladium (Pd)-decorated multiphase composite electrode (TiN/Ti1.886O3/MgTiO3/Mg2TiO4) denoted as Pd@MPC. The synergistic coexistence and contact between these phases improved the electrochemical performance of the material and provided complementary properties such as electrical conductivity (from TiN and Pd), chemical stability (of MgTiO3), and surface reactivity (of Ti1.86O3 and Pd), which are crucial for efficient electroanalytical applications. The electrode material was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM), which confirmed the successful incorporation of Pd nanoparticles and significantly improved the catalytic properties. Pd, which is known for its excellent electrocatalytic activity, especially in oxidation reactions, facilitates the electrochemical detection of pesticides such as DIC and 2,4-D. The Pd nanoparticles likely serve as active sites for the oxidation of pesticides and improve the sensitivity and selectivity of the sensor. Voltammetric analyses showed that the Pd@MPC/GC electrode exhibited significantly better electrocatalytic activity compared to a commercially available glassy carbon electrode. The results showed that pH strongly influenced the signal-to-noise ratio, with optimal analytical performance achieved at pH 2.0. The developed method showed linearity within a concentration range of 4.99 to 53.82 ng/mL, with correlation coefficients of r = 0.998 for DIC and r = 0.990 for 2,4-D, and a detection limit of 3.03 ng/mL. Recovery tests in river water samples showed a recovery rate of 101%, which is consistent with the results of the HPLC/DAD method used as a comparative method. These results underline the effectiveness of the Pd@MPC/GC electrode for environmental monitoring applications
Necessary Optimality Conditions for Lyapunov-Type Optimization Problem with State Constraints
No full textThis paper investigates a Lyapunov-type optimization problem incorporating an inequality integral constraint and a phase inequality constraint, both defined in L∞([0,T],Rn). The problem is approached directly using a theorem of the alternative, assuming differentiability, to derive necessary optimality conditions. Unlike earlier works, such as a nonsmooth convex isoperimetric problem with phase constraints or problems excluding phase constraints, this study focuses on a smooth case of problem. The problem formulation is motivated by the growing interest in continuous-time linear and nonlinear optimization problems, a field originally explored by Bellman (Proc Natl Acad Sci USA, 39:947–951, 1953). Building on prior results where new Karush–Kuhn–Tucker (KKT) conditions were introduced for problems with inequality constraints, this work extends the scope by incorporating an integral constraint into the analysis. The manuscript outlines the problem’s preliminaries, introduces a regularity condition for systems of inequalities, and presents a theorem of the alternative as the foundation for deriving the main results. Necessary optimality conditions are established and illustrated with an example, while the application of computational methods demonstrates how these conditions contribute to finding optimal solutions. By utilizing recent advancements in theorems of the alternative, this paper contributes to the theory of continuous-time programming problems in both finite-dimensional and infinite-dimensional spaces. The findings highlight the importance of integrating analytical and computational approaches to address these increasingly relevant optimization challenges
Kinetic Analysis of the Reaction of Silver with Elemental Sulfur in Mineral Insulating Oil
No full textElemental sulfur (S8) reacts readily with silver, forming highly conductive silver sulfide on
silver-coated components of on-load tap changers (OLTCs), forming a highly conductive
silver sulfide film at the surface of an OLTC, which can lead to the failure of critical
components in power transformers. This study investigates the reaction between metallic
silver and elemental sulfur dissolved in mineral insulating oil across temperatures from
60 ◦C to 180 ◦C. The process involves three stages: the diffusion of sulfur through oil,
surface reaction, and product diffusion. For low-viscosity oil, diffusion is not the limiting
factor, and sulfur does not react immediately on the silver’s surface, suggesting possible
adsorption or intermediate formation. A kinetic analysis revealed that the reaction follows
first-order kinetics, with a change in mechanism above 150 ◦C. The reaction follows the
Arrhenius equation in two separate regions: 60–150 ◦C and 150–180 ◦C. Activation energy
was calculated as 23.67 kJ mol−1
, and it can be concluded that the reaction is controlled by
the diffusion of sulfur through mineral oil, and at higher temperatures (150 ◦C to 180 ◦C),
the calculated activation energy is 160.69 kJ mol−1
, which leads to the conclusion that the
combined chemisorption and diffusion through a silver sulfide–oil interface becomes the
new limiting factor