Spectrophotometry is widely favored for iron detection due to its simplicity, speed, cost-effectiveness, and versatility. Conventional methods rely on synthetic chromogenic reagents, which often involve toxic chemicals, hazardous solvents, and significant waste generation. Natural plant extracts offer a sustainable solution, being less toxic, easier to prepare, and more environmentally benign than synthetic counterparts. This study introduces a simple, green, and cost-effective spectrophotometric method for iron determination using oak bark extract as a natural, selective reagent. The approach relies on the development of a reddish-brown colored complex (ëmax = 550 nm) when iron ions react with oak bark extract in a neutral acetate buffer solution (pH 7.0). Under optimized conditions, the assay demonstrated excellent linearity in the range of concentrations 0.56 – 5.6 ìg/mL (R2 = 0.998) with high molar absorption coefficient (0.55 × 104 L/mol/cm), good sensitivity (LOD = 57.4 ng/mL, LOQ = 191.5 ng/mL), and precision (RSD < 5%). Statistical validation through t-test and F-test comparisons with 1,10-phenanthroline method confirmed the accuracy and reliability of the proposed method at 95% confidence levels. The assay showed remarkable selectivity for Fe (II) against various interfering cations. The proposed method was successfully applied for iron determination in blood serum and various pharmaceutical preparations, with a high recovery rate ranging from 98.01 to 103.38%.

This study presents an investigation into the effects of key process parameters on the encapsulation of betamethasone acetate (BA) in poly(lactic-co-glycolic acid) (PLGA) microspheres. The Taguchi method was employed to identify the most influential factors affecting microsphere characteristics. The experimental design included variation of several parameters: PLGA concentration, BA concentration, the aqueous-to-organic phase ratio and stirring speed. The results indicate that BA loading is primarily influenced by its own concentration and the polymer concentration. High-performance liquid chromatography was used for determination of betamethasone acetate. Optimal loading was achieved at PLGA and drug concentrations of 100 and 20 mg/mL, respectively, an aqueous-to-organic phase ratio of 50:1, and a stirring speed of 500 rpm. Under these conditions, the drug loading reached 4.35%, compared to 1.44% prior to optimization. These findings may support the refinement of PLGA microsphere preparation techniques for other active pharmaceutical ingredients with similar physicochemical properties.

Amperometric sensors coated with MIPs were created for the determination of cefazolin sodium (Cef), neomycin sulfate (Neo) and sulfanilamide (Sulf) in liquid media with detection limits 1.5 × 10^–6, 7.2 × 10^–6, and 4.7 × 10^–6 g/dm³, respectively, which are below the maximum permissible concentrations of these antibiotics. The relative standard deviation (S_r) is less than 4%, which indicates a high accuracy of the determination. The sensors demonstrated high selectivity with an imprinting factors (IF) 5.8 – 6.3 for the target compounds and low IF (<1.3) for other antibiotics. The accuracy and precision of MIP-Cef, MIP-Neo, and MIP-Sulf sensors was evaluated in the analysis of model solutions by the recovery test with S_r not exceeding 5%, and by the reference methods of spectrophotometry and HPLC. The statistical analysis (F-test and t-test) did not reveal significant differences, confirming the reliability of the method. The absence of the influence of other antibiotics on the results of Cef, Neo, and Sulf determination using MIP sensors was proved by analyzing model mixtures containing cefotaxime, ceftriaxone, and streptomycin. MIP sensors were tested in the analysis of cow milk: in all samples analysed residual content of all antibiotics (Cef, Neo, and Sulf) was not detected. Thus, the developed MIP sensors possess high sensitivity, selectivity, and accuracy, making them promising for monitoring antibiotic residues in water and food products.

Using ceramic technology can lead to the formation of rigid agglomerates of particles, which hinder uniform sintering and the production of high-density ceramics. This work presents the results of a study on α-Al₂O₃ powder. The main focus was on the influence of milling and centrifugation parameters on the final particle size when adding NH₄OH for electrostatic stabilization, which prevents agglomeration. The analysis of the dependence of the centrifugate yield on centrifugation conditions (number of revolutions, content of α-Al₂O₃) allows for the optimization of technological parameters to achieve conditions for the highest yield of particles of a specified size. Particle size was assessed using dynamic light scattering, which also enables the determination of the particle size distribution, necessary for studying material properties. Additionally, the grinding time required to achieve a particle size of 0.4 μm was calculated, and the value of the grinding rate constant was determined. Furthermore, for particles around 0.4 μm in size, the fulfillment of sedimentation-diffusion equilibrium without centrifugation was evaluated. The obtained results can be used to improve methods for producing high-quality α-Al₂O₃ powder, which is widely used in various industries (in the production of ceramics, electronics, catalysts, etc.).

When assessing the operation of interfield gas pipelines on frozen ground, the efficiency of their electrochemical protection (ECP) is analyzed, among other things. The paper presents the results of the study of anomalies in the ECP of underground pipelines operated in frozen ground conditions. Computer mathematical modeling methods were applied, laboratory experiments were conducted using a test rig. Using computer modeling, the key factors contributing to the acceleration of corrosion processes were identified: the formation of a water layer around the pipeline during ground freezing and shielding of the protective potential of ECP, which leads to a local increase in the corrosion rate. It has been experimentally confirmed that at the temperature of transported gas above 0°C and in the presence of frozen ground ECP loses its efficiency due to potential distribution disturbance. It is shown that the use of an auxiliary anode increases the homogeneity of the protective potential and eliminates the shielding effect of frozen ground. The obtained results can be used for optimization of ECP systems in cryolithozone to reduce the risk of accidents in pipeline transport.

One of the promising and widespread methods of powder metallurgy is hot isostatic pressing (HIP), which makes it possible to obtain dense, non-porous workpiece from metal powders with enhanced mechanical characteristics. However, due to the uneven distribution of temperature and pressure during the casting process, an inhomogeneous structure is formed from the periphery to the center of the workpiece, which negatively affects the further operation of the finished product. The paper presents the results of a study of the structure and properties of a blank made of Ti-6Al-4V titanium alloy obtained by the HIP method. Metallographic analysis was performed, and the distribution of microhardness, density, and porosity over the sample section was analyzed. It is established that the structure of the material formed during the HIP process is heterogeneous, and its properties change from the periphery to the center (microhardness and porosity increase, density decreases). It is shown that the reason for the uneven formation of mechanical properties is the presence of a gradient in the volume fraction of the β-phase, while its content in the material of the peripheral part of the workpiece is ~20%, and in the central part — 28%. The results obtained can be applied in assessing the quality of the obtained HIP workpieces made of Ti-6Al-4V titanium alloy, as well as to create computational models of HIP technological processes.

The paper considers a technique for assessing the strength of a material in a complex stress-strain state. For this purpose, the strength of disk-shaped material samples with stress concentrators is being investigated. Stress-strain state modeling was implemented in this work using the finite element method, taking into account the nonlinear nature of the processes under consideration. The reliability of the obtained numerical simulation results was evaluated on the basis of a sequence of FE approximations. The experimental destruction of the proposed samples was carried out on a typical Instron 5989 machine and confirmed the possibility of creating in the tested samples a given level of the ratio of the main stresses arising under biaxial tension conditions. Using the example of steel 45, it is shown that the use of the samples under consideration makes it possible both to evaluate the structural strength of materials and to carry out a local approximation of the corresponding marginal surface. A modified version of the Pisarenko – Lebedev criterion was used as the theoretical basis for its local approximation. It is shown that the proposed disk samples have a relatively simple shape and have a high variability in the type of stress state. This circumstance allows us to transfer the assessment of the structural strength of materials to the stage of its laboratory studies.

In ultrasonic testing, equipment calibration typically relies on signals scattered from artificial defects of predefined shape. However, the characteristics of the notches commonly used for this purpose strongly depend on the manufacturing method. This study presents the results of investigating the scattering of longitudinal and shear waves on crack models using notches fabricated by conventional methods (milling and electrical discharge machining) as well as laser cutting. Additionally, model cracks produced by friction stir welding were examined. Defect detection was carried out using the Time-of-Flight Diffraction (TOFD) technique. The paper presents comparative analysis data of signals diffracted at the tips of planar defect models and evaluates tip coordinates and defect type based on the amplitude of the recorded signal. The influence of the rotation angle of the transmitter-receiver pair relative to the crack model on the amplitude of ultrasonic waves scattered at the artificial reflector tip was also analyzed. Measurements were performed at frequencies of 5 and 10 MHz during both longitudinal scanning (along the reflector) and transverse scanning (parallel and perpendicular to the weld axis). The results show that laser cutting provides the most accurate crack-tip simulation. This method enables the fabrication of planar defect models that closely resemble real defects, with tip openings on the order of 0.01 mm. The findings can be applied in the fabrication of artificial defects in calibration samples for ultrasonic inspection.

Currently, there is no generally accepted standard setup for measurements the fatigue limits of biomedical magnesium alloy samples in corrosive environments. Usually every research group uses assemble its own testing system, which does not always take into account many technical factors that significantly affect the final result of the experiment. In this paper, we propose a setup that can be assembled on the basis of a standard fatigue machine for measurements the corrosion-fatigue durability of bioresorbable magnesium alloys in various physiological solutions. It’s main components include: a testing machine with a slot plate required for rigid attachment of the chamber; polyamide grips providing galvanic isolation; a peristaltic pump for pumping the medical solution used; an ionometer connected to a computer to record changes in pH and temperature; a thermostat to maintain the temperature in the chamber within a given range; an additional solution fed into the chamber through a needle using a small peristaltic pump when a given pH level is exceeded, which allows maintaining the pH within the acceptable range of values. The setup uses corset-type samples, although other options are also acceptable, and provides the ability to install a camera to visualize corrosion processes on witness samples. The test system allows achieving good repeatability and reliability of the obtained results, which was experimentally verified and confirmed on magnesium alloy MA14 of different melts, selected as a model. The proposed setup can be used to assess the fatigue life of magnesium alloys for medical purposes. It is not difficult to implement in ordinary factory laboratory conditions.

This article provides an overview of modern scientific support systems (SSS), which increases the effectiveness of scientific activity of specialists due to timely receipt of relevant publications. Special attention is paid to the application of SSS in rapidly changing subject areas, in particular Computer Science. The main approaches to the creation of SSS are outlined, it is noted that the key direction of the development of SSS is the personalization of information search and analysis. One of the main ways to implement a personal approach is to build a user profile (PP). Various technologies are used for this purpose. This paper shows the advantages of constructing PP based on keywords (KW) — unigrams, bigrams, trigrams and n-grams. This allows to create a reliable «information portrait» of the text, to obtain a compressed semantic core for it. KW describe short documents most effectively and are well suited for analyzing bibliographic descriptions of scientific articles that include titles, annotations (and other supporting sections). The paper makes a formal statement of the task of extracting KW from scientific documents, systematizes methods for detecting KW, and justifies the choice of the neural network model KeyBERT for practical use in SSS. The high versatility of the KeyBERT and its effectiveness for detecting KW in short scientific texts are noted. An algorithm implementing KeyBERT is given (embedding vectors are based on the RoBERTa model). To demonstrate the capabilities of the developed SSS (in particular, the construction and updating), research was conducted on a sample of «UIT-2024», formed at the Department of Control and Intelligent Technologies of the Moscow Power Engineering Institute. It includes 10,000 documents on ten topics in the field of Computer Science. After additional learning, the KeyBERT algorithm extracts informative KW from this sample and automatically generates an expanded list of one-word and multi-word descriptors that allow the specialists to form and update their profiles, increasing the relevance of recommendations in the SSS. The possibilities of the proposed approach are considered in detail using the example of a hypothetical specialist in Computer Science.