Composite Action Research Articles

EVALUATING THE STRUCTURAL EFFICACY OF ANGLE AND CHANNEL SHEAR CONNECTORS IN BRICK AGGREGATE CONCRETE AND STONE AGGREGATE CONCRETE AND COMPARISON

Composite structure is becoming prominent for its economy, less time consumption, and higher stiffness-mass ratio. Composite action of the steel-concrete composite structure mainly depends on the connector's geometry and materials. Proper choice of shear connector could make steel beam and concrete slab cross-section minimal. This study carries out push-out tests to evaluate the structural efficiency of channel and angle shear connectors in brick aggregate concrete and stone aggregate concrete. It specifically looks at the failure mode, ductility, load-slip behavior, and energy absorption capacity. In brick aggregate concrete, results show that under monotonic loading, channel connectors have been found to have 15.27% more shear capacity & 28.38% more slip than angle connectors. Similarly, in stone aggregate concrete, channel connectors have been found to have 14% more shear capacity & 12.97% higher slip than angle connectors. On average, stone aggregate concrete has been found to have 34.84% higher shear capacity and 6.7% greater slip than brick aggregate concrete. Strain energy and plastic energy were found 78% and 17.6% less in brick aggregate specimens than those in stone aggregate specimens, respectively. Experimental results were slightly lower for both shear connectors than the empirical values.

Construction of a sensor array using TiO2 NRs/CuO/rMIP with imprinted sites regulation as light-activated nanozyme to colorimetric detect fluoroquinolones

Fluoroquinolone antibiotics are widely used in daily life, but their abuse has caused serious problems, so it is very important to detect fluoroquinolones accurately and conveniently. In this study, a light-activated nanozyme sensor array (TiO2 NRs/CuO/rMIP) was prepared, and principal component analysis (PCA) was employed for qualitative and quantitative determination of four fluoroquinolones in water environments. The photoactive sites of TiO2 were determined by photo-deposition of CuO, and the molecularly imprinted sites was anchored to the photoactive site by the composite action between antibiotic templates and CuO, which led to the consistent adjustment of the imprinted sites and photoactive sites, thus enhancing the enzyme-like activity of TiO2 NRs/CuO/rMIP. In Addition, by adjusting the types and proportions of antibiotic templates during the preparation of MIP, TiO2 NRs/CuO/rMIP sensors with different response signals to four fluoroquinolones were prepared, and a sensor array was established based on them. Through an RGB analysis system of smart phone and PCA analysis method, qualitative and quantitative detection of the four fluoroquinolones was realized. The detection range of the four antibiotics was 0.1–3000 μM, which showed a good prospect for the actual detection of antibiotics.

Shake‐table tests on steel moment‐resisting frames with detachable yielding zones

AbstractThis article presents an experimental campaign based on shake table tests conducted as part of the European research project FUTURE, funded in the framework of the H2020‐INFRAIA SERA program. Three steel moment‐resisting frame structures equipped with replaceable dissipative elements were tested. The experimental mockups were scaled two thirds from a reference building archetype designed per the latest draft of the upcoming version of Eurocode 8. Each mockup has different bolted end‐plate beam‐to‐column joints, namely reduced beam section (RBS), extended stiffened endplate (ESEP), and Haunched types, designed with European seismic prequalification rules. Additionally, detachable column segments at the base were designed with Reduced Column Sections (RCS) to localize the plastic deformation and enforce the intended global dissipation mechanism. The slab was detailed with reduced areas around the columns to minimize the direct composite action at beam‐to‐column joints. The mockups were subjected to incremental near‐field excitations with combined horizontal and vertical components. In this article, the experimental campaign is first described, providing details on the mockup's geometry, design, scaling, ground excitations, and sensor distribution. Then, the observed global and local responses are discussed. The results demonstrate that the global response of the mockups was significantly influenced by the type of beam‐to‐column joints, which exhibited the expected damage. The RCS configuration in the column bases also showed satisfactory behavior without leading to local or global instabilities throughout the performed tests.

Bending test of long-span ultra-shallow floor beam (USFB) with two lightweight concretes

This paper presents the bending behaviour of a partially encased ultra-shallow floor beam (USFB) with two types of lightweight concrete. The beam was fabricated by welding two asymmetric Tees together along the web to create a beam with multiple circular openings that act as ‘plug shear connectors’ with the concrete encasement. The bending resistance of the plug-shear connection system was obtained by testing a composite USFB for a beam span of 7.2 m, half of the span being made with a lightweight concrete slab and the other half span with an ultra-lightweight concrete slab. Analysis of the four-point bending tests was carried out to determine the increase in bending resistance due to composite action and the contribution of the longitudinal shear connection due to the concrete plug passing through the web openings combined with additional tie bars. Calculations of the properties of the USFB with the two types of lightweight concrete were made according to SCI documentation and Eurocode 4. It was observed that the deflections were predicted accurately by the elastic properties and that the failure mode was by concrete crushing before the plastic bending resistance of the composite section had been developed. It was also shown that the cracked section properties should be used for the deflection analysis.

Experimental investigations on the partially concrete-filled steel tubular slender beams

This paper focuses on the flexural behaviour of partially concrete-filled steel tubular (PCFST) beams having slender cross-sections (D/t > 150). PCFST beam is developed by optimising the tension zone concrete in a concrete-filled steel tubular (CFST) beam. Twelve specimens were investigated under a four-point load to understand the flexural behaviour and load transfer mechanism of PCFST slender beams. Parameters considered for the tests are concrete compressive strength, shear-span-to-depth ratio, and concrete wall thickness. The failure mode, load-deflection, strain distribution and moment-rotation data of the test specimens are reported and compared. In general, PCFST beams exhibit the same flexure behaviour as CFST beams in terms of flexural resistance and stiffness, and the weight reduction is around 40 %. However, composite action is lost in PCFST without tension zone concrete, and the beam behaves like an empty steel tube. Therefore, a minimum concrete wall thickness (tc,min) in the tension zone is required in PCFST and an equation for tc,min is proposed based on the test results. Concrete compressive strength is found to have lesser significance in the PCFST beam, whereas a decrease in the shear span-to-depth ratio from 2 to 1 can alter the mode of failure from flexure to shear. A numerical model is developed using ABAQUS to support the test results. This study finds the PCFST beam an optimised replacement for CFST beams in flexure-predominant structural systems. Additionally, a flexure capacity equation is proposed using the plastic stress distribution method, and made good predictions with the experimental and finite element results.

GR‐Former: Graph‐reinforcement transformer for skeleton‐based driver action recognition

AbstractIn in‐vehicle driving scenarios, composite action recognition is crucial for improving safety and understanding the driver's intention. Due to spatial constraints and occlusion factors, the driver's range of motion is limited, thus resulting in similar action patterns that are difficult to differentiate. Additionally, collecting skeleton data that characterise the full human posture is difficult, posing additional challenges for action recognition. To address the problems, a novel Graph‐Reinforcement Transformer (GR‐Former) model is proposed. Using limited skeleton data as inputs, by introducing graph structure information to directionally reinforce the effect of the self‐attention mechanism, dynamically learning and aggregating features between joints at multiple levels, the authors’ model constructs a richer feature vector space, enhancing its expressiveness and recognition accuracy. Based on the Drive & Act dataset for composite action recognition, the authors’ work only applies human upper‐body skeleton data to achieve state‐of‐the‐art performance compared to existing methods. Using complete human skeleton data also has excellent recognition accuracy on the NTU RGB + D‐ and NTU RGB + D 120 dataset, demonstrating the great generalisability of the GR‐Former. Generally, the authors’ work provides a new and effective solution for driver action recognition in in‐vehicle scenarios.

Capacity design assessment of composite reduced web section (RWS) connections

A gap in current design approaches demands explicitly introducing a capacity design approach when designing steel-concrete composite reduced web section (RWS) connections. This paper addresses this gap by presenting test-validated finite element models and parametric investigations, focusing on the presence and absence of composite action over the web opening, the diameter, and the end-distance of the web opening. Additionally, the first-ever comprehensive experimental and numerical database from the literature on bare steel and composite RWS connections is compiled and thoroughly analysed to develop the capacity design assessment for such connections. Both parametric investigations and the database highlight the significance of the capacity design ratio between the connected components in achieving a desirable ductile mechanism. This is crucial, as evidenced by the results: a 15 % increase in the connection's moment capacity led to an average 21 % difference in dissipated energy, favouring the web opening with a diameter of 50do over 80do, in RWS connections with the presence of composite action. The results show that proper consideration of the capacity design approach in designing RWS connections ensures a stable yield mechanism is developed, resulting in the redistribution of global action and capping deformation demands on non-ductile elements. This enhances connections' rotational capacity and ductility by forming the Vierendeel mechanism. Lastly, the paper presents a detailing recommendation for employing RWS connections in both existing and new structures for seismic purposes.

Corrosion Protection of Embedded Steel Reinforcement Using Canarium Schweinfurthiia Exudate for Coastal Concrete Structures

This experimental study evaluated the effects of corrosion on the bond behavior and structural integrity of reinforced concrete. A total of 36 concrete cube specimens containing reinforcing steel bars were divided into control, uncoated, and Canarium schweinfurthiia exudate/resin coated groups and immersed in 5% NaCl solution for 360 days. Periodic tests were conducted to analyze corrosion levels, bond strength, steel bar properties, and failure loads. Results showed the control specimens exhibited little corrosion while uncoated bars experienced significant corrosion after exposure. In contrast, exudate/resin coated bars demonstrated a substantial reduction in corrosion, indicating the coating's inhibitory effects. Pull-out bond strength and maximum slip tests consistently revealed lower strengths and higher slips in corroded samples compared to controls. However, coated specimens maintained higher bond capacities and lower displacements, validating the coating's protective performance. Measurement of bar diameters, cross-sectional areas, and weights before and after corrosion highlighted the proportional losses associated with the corrosion process. Dimensions and masses of corroded reinforcements decreased by 2-7% on average from initial values. In comparison, controls showed minimal variations. Failure load analyses found controls withstood the highest loads, while corroded members exhibited reduced capacities. Overall, the study demonstrated corrosion negatively impacts the critical steel-concrete bond and undermines composite action essential for structural integrity. Exposure to NaCl solutions markedly increased corrosion and decomposition of unprotected bars. However, natural Canarium schweinfurthiia exudate/resin coatings were highly effective at mitigating corrosion effects by preserving bond strength, slip resistance, steel geometries and load capacities close to uncorroded levels. The findings validate protective coatings as a viable solution for durable reinforced concrete design in marine environments. Proper corrosion prevention through coatings or inhibitors can help ensure structures withstand service loads over their design life.

A Critical Review of Cold-Formed Steel Built-Up Composite Columns with Geopolymer Concrete Infill

Concrete-filled built-up cold-formed steel (CFS) columns offer enhanced load-carrying capacity, improved strength-to-weight ratios, and delayed buckling through providing internal resistance and stiffness due to the concrete infill. Integrating sustainable alternatives like self-compacting geopolymer concrete (SCGC) with low carbon emissions is increasingly favoured for addressing environmental concerns in construction. This review aims to explore the current knowledge regarding CFS built-up composite columns and the performance of SCGC within them. While research on geopolymer concrete-filled steel tubes (GPCFSTs) under various loads has demonstrated high strength and ductility, investigations into built-up sections remain limited. The literature suggests that geopolymer concrete’s superior compressive strength, fire resistance, and minimal shrinkage render it highly compatible with steel tubular columns, providing robust load-bearing capacity and gradual post-ultimate strength, attributed to the confinement effect of the outer steel tubes, thereby preventing brittle failure. Additionally, in built-up sections, connector penetration depth and spacing, particularly at the ends, enhances structural performance through composite action in CFS structures. Consequently, understanding the importance of using a sustainable and superior infill like SCGC, the cross-sectional efficiency of CFS sections, and optimal shear connections in built-up CFS columns is crucial. Moreover, there is a potential for developing environmentally sustainable built-up CFS composite columns using SCGC cured at ambient temperatures as infill.

Numerical simulation of steel-concrete composite beams and slabs at elevated temperatures

Steel-concrete composite beams with shear studs providing composite action between the concrete slabs and steel beams are widely used in modern steel-framed building construction. Three-dimensional finite element modelling has been a viable option for investigating the fire behaviour of composite beams. Although many finite element models are available in the open literature, most of them are simplified models verified by limited test data. Meanwhile, early test data often did not have all the required information for finite element simulation, and some assumptions need to be made. But more detailed test data are now available in the open literature for steel-concrete composite beams, which can be used to develop a generalised finite element model. In addition, National Institute of Standards and Technology has proposed new stress-strain models for steels at elevated temperatures, which can be compared with the more widely adopted Eurocode 4 steel material models in simulating composite beams. Accordingly, this paper selected 22 specimens, including two reinforced concrete slabs, 12 composite beams with reinforced concrete slabs, two composite slabs with profiled steel sheeting, two steel-concrete composite push test specimens with profiled steel sheeting, and four composite beams with profiled steel sheeting, from nine references to verify the developed finite element model. The proposed finite element model can capture different failure modes of composite beams, such as steel yielding/local buckling, concrete cracking/crushing, debonding of profiled steel sheeting, and stud fracture, which is crucial to comprehend the composite beam behaviour at elevated temperatures.

Volatile oil constituents, antioxidant and antibacterial activities of Lonicera caprifolium L. in different areas of Iran

The genus of Lonicera is the largest genus of Caprifoliaceae family. This study revealed the composition, antioxidant, and antibacterial actions of essential oils of Lonicera caprifolium L. in different areas of Iran; Qom, Mashhad, Shiraz. Gas chromatography-mass spectrometry examination was applied to recognise the oil conformation. The essential oils of Qom included a high number of monoterpenes, with linalool as the significant constituent. In the essential oil of Mashhad, the main elements were methyl linoleate. The essential oil of Shiraz displayed a similar profile, including a large quantity of fatty acid, with methyl palmitate as the main component. The antioxidant activity was assessed via the DPPH exam, and the antimicrobial action was verified using the broth microdilution procedure. The essential oils of Qom revealed the maximum antimicrobial and antioxidant actions between the three regions, ascribed to its high concentration of monoterpenes and phenolic composites. Moreover, principal component analysis (PCA) and heat map successfully revealed the variation and correlation between metabolites of the three oils. These conclusions highlight the potential of L. caprifolium as natural foundations of antimicrobial and antioxidant representatives, with investigation required to reveal their therapeutic requests.

Evaluation of shear performance of timber-timber composite joints

The mechanical performance of timber composite floors is influenced by the degree of composite action between the components. In this study, the shear strength performance of cross-laminated timber and glued laminated timber composite floors based on the joining method was evaluated by push-out test. Eight types of timber-timber composite joints were evaluated using three different methods: lag screw joints, glued-in rod joints using fully threaded bolts and glass fiber reinforced plastic, and hybrid joints. Strength characteristics were derived to make theoretical predictions on the load-carrying capacity of the joints. The results showed that the glued-in rod joints were superior to the lag screw joints, with slip coefficients and ductility measured as 10 times and 2.5 times higher, respectively. The reliability of the strength characteristics of the glued-in rod joints was remarkably different depending on the presence or absence of anti-adhesive tape applied to the timber-to-timber joint surface. The load capacity of the hybrid joint, which combines mechanical and glued-in rod joining methods, was 47% higher than that of the lag screw joint and 38% higher than that of the glued-in bolt joint. In the European Yield Model modified to estimate the load capacity of joints, the rope effect and the yield moment of the fasteners had a remarkable impact on the predicted load capacity.

Prospects for the Application of Nephroprotectors of Plant Origin Based on Lespedeza bicolor

Chronic kidney disease is a significant risk factor for the development of various non communicable diseases, including cardiovascular diseases. Every year there is a tendency to increase the number of patients with urinary system diseases. Chronic kidney disease is a global medical and social problem that leads to early disability of the working population. Today, scientists are focusing considerable attention on the search for new drugs with hypo azotheamine activity, as it is important to slow down the progress of chronic kidney disease. Herbal medicines are promising for the prevention and treatment of such pathologies. Plants with proven significant hypo-azotemic activity and safety include representatives of the genus Lespedeza, in particular, Lespedeza capitata and Lespedeza bicolor. The objective: to review the literature on the chemical composition and biological action of Lespedeza capitata, Lespedeza bicolor and the prospects for the use of a domestic medicinal product based on the herb Lespedeza bicolor as a hypoazotemic agent. Results. According to the literature, the chemical composition of Lespedeza capitata and Lespedeza bicolor differs slightly and is represented by flavonoids, procyanidins, hydroxycinnamic acids, etc. The therapeutic effect of these plants is associated primarily with the glycosides quercetin, luteolin (isorientin, vitexin) and kaempferol (robinin). It has been found that the complex of biologically active substances included in the preparation has nephro- and hepatoprotective, hypo-azotemic, antidiabetic, anti-inflammatory and diuretic effects and is promising in the treatment of many diseases of the urinary system. Conclusions. Literature sources indicate that the extracts from the shoots of Lespedeza capitata and from the herb Lespedeza bicolor are similar in chemical composition and pharmacological properties. Ethanol extracts based on Lespedeza capitata and Lespedeza bicolor have a long history of use and are characterised by proven hypo-azotemic, nephroprotective and anti-inflammatory effects. They are successfully used for the prevention and treatment of chronic renal failure, acute and chronic nephritis and extrarenal azotemia. The complex of biologically active substances contained in herbal remedies helps to increase renal filtration, reduce azotemia, increase diuresis, enhance sodium excretion and, to a lesser extent, potassium excretion.

An integrated investigation into the antibacterial and antioxidant properties of propolis against Escherichia coli cect 515: A dual in vitro and in silico analysis

Urinary tract infections resulting from Escherichia coli, are prevalent and have become increasingly difficult to treat due to antibiotic resistance. This study aimed to explore the potential of propolis extract from beehives in Algeria’s Tiout region as a natural antibacterial agent against E. coli CECT_515. The phytochemical composition, antioxidant activity, and antibacterial action of the extract has been evaluated and compared to four synthetic antibiotics, both in vitro and in silico. The propolis extract had high levels of total polyphenol and total flavonoids, regarding its antioxidant properties, the extract showed an important ability of DPPH radicals scavenging, as determined by its IC50 value of 330.08±13.35 μg/mL. The excerpt showed important antibacterial efficacy against Escherichia coli, as demonstrated with important inhibition zones. The extract’s inhibitory effects were compared to four synthetic antibiotics, including gentamicin, pipemidic acid, cefazolin, and colistin, molecular docking analysis revealed that the propolis extract interacted with the active site of beta-lactamase, a protein responsible for antibiotic resistance, and showed binding affinities and conformational stability during molecular dynamics simulation for 250 ns. Overall, the results suggest that the propolis has significant antioxidant and antibacterial properties and could serve as a promising natural alternative to synthetic antibiotics for the treatment of E. coli infections.

Numerical simulation of axially loaded circular concrete-filled steel tubular short columns with localized corrosion

Concrete-filled steel tubular (CFST) columns are widely utilized in structures owing to their cost-effectiveness, high strength, ductility, and proven fire resistance. Despite these advantages, concerns persist regarding the performance of CFST columns with locally corroded steel tubes, impeding their widespread adoption in offshore structures. This research employs three-dimensional finite element (FE) simulations for circular CFST stub columns subjected to axial compression, validated against experimental data. Verification includes full load-displacement histories, ultimate axial strengths, and failure modes. The validated FE models are then employed to assess and compare the structural behavior of CFST columns with various shapes of localized corrosion, analyzing overall load-deformation curves, interaction stress-deformation responses, and composite actions. To acquire critical data for understanding stub column behavior, 81 specimens underwent non-linear finite element analysis, with local corrosion represented by artificial notches in steel tubes. Test parameters, such as notch orientations, lengths, depths, widths, and concrete compressive strength, are varied. Results elucidate the impacts of these parameters on different aspects of stub column responses with corroded steel tubes. Furthermore, the accuracy of existing design models in predicting the ultimate axial strengths of CFST columns with corroded steel tubes is assessed. Finally, through parametric analysis of test results, a practical model is proposed and verified for computing the peak resistance of a CFST stub column with a locally corroded steel tube.

Experimental and numerical studies of mechanical performance of an assembled friction type structural underpinning joint

This paper proposed an assembled underpinning joint (UPJ) based on the interfacial friction action between the underpinned concrete member and the underpinning steel beams (UPSBs). To investigate the mechanical performance and failure modes of the proposed UPJ, 20 specimens with different concrete strengths were fabricated and tested with varied preloading levels. Experimental results showed that the proposed UPJs could effectively transfer the vertical loads in the concrete columns through the friction action and all specimens failed due to the slip between the underpinned concrete column and the UPSBs. The failure loads of the specimens were in a positively linear relationship with the preloading levels and an interfacial friction coefficient of 0.46 was found. Numerical models were also created to further examine the detailed structural behaviours of each components in the UPJs, which confirmed that, the UPSBs were subjected to a composite action mainly combining both bending and torsion. The frictional stresses between the UPSBs and the concrete column were concentrated in the regions of the web of UPSBs near flanges and stiffeners. The load transfer mechanisms of the proposed UPJs under complex loading conditions were clarified. The damages, occurred at the corners of concrete columns due to high stress and strain concentrations, should be alleviated or prevented by protective measures in practice.

Study on Microscopic Characteristics and Rock Mechanical Properties of Tight Sandstone after Acidification–Supercritical CO2 Composite Action: Case Study from Xujiahe Formation, China

Acidified CO2 fracturing is a viable method for increasing production in deep, tight sandstone reservoirs. However, the potential mechanism of changes in pore structure and mechanical properties of sandstone under acidified CO2 supercritical composite is not clear. Understanding this mechanism is important for the study of crack initiation and extension in tight sandstone reservoirs. This study utilizes sandstone samples from the Xujiahe Formation reservoir in Rongchang District as experimental specimens. The primary focus is to analyze the changes in pore structure and mechanical properties of these samples after acidification–supercritical CO2 composite action. Nuclear magnetic resonance (NMR) and uniaxial compression tests are employed as the main investigative techniques. The results show that there was a physicochemical synergy between the acidification–supercritical CO2 composite effect; the crack initial stress, damage stress, and peak stress of the sandstone after 16 MPa supercritical CO2 acidification treatment were reduced by 20%, 49.5%, and 49.8%, respectively; the crack volumetric strain accelerated and the sandstone evolved from brittle to ductile damage; and the larger pore space and microcracks of the sandstone increased significantly after the treatment, which can be attributed to the gradual dissolution of intergranular cement leading to the formation of new pores connected to the existing pore network. The change mechanism of sandstone after acidification–supercritical CO2 compound treatment is also proposed.

A Numerical Study on Predicting Bond-Slip Relationship of Reinforced Concrete using Surface Based Cohesive Behavior

Overall structural integrity and load transfer between concrete and reinforcement enabling composite action relies on the bond between concrete and reinforcement. Bond strength determination of reinforced concrete is an essential task that a pullout test can determine. Experimental pullout behaviour can be affected by various parameters, such as concrete and steel strength, boundary conditions, etc. Therefore, a parametric study on pullout tests is time-consuming. In addition, measurements of internal stress-strain components and damages of constitutive materials are also difficult in experimental endeavours. In this context, finite element (FE) models should be developed to perform a parametric study with cost and time-saving. This study proposes a finite element modeling strategy of reinforced concrete under pullout force by using the expected failure mechanism to predict bond-slip behaviour in ABAQUS. In FE models, surface-to-surface cohesive interaction behaviour was used to assign interaction between reinforcement and concrete. The proposed modelling strategy was validated with available experimental data from four reference specimens, having all possible failures (i.e., pullout, splitting, and splitting-pullout) under pullout loading. The finite element analysis showed that the proposed FE modeling strategy performed well in predicting bond-slip behaviour in elastic regions. Additionally, maximum bond stresses were predicted satisfactorily, except for the splitting failure pattern, using the proposed FE modelling strategy.

Isolation, identification and quantification of flavonoids from the flowers of <i>Staphylea pinnata</i> L.

Introduction. Search for new plant species containing biologically active substances (hereinafter – BAS) is one of the leading tasks of pharmacognosy as a science. The search for flavonoid glycosides in plant raw materials is especially relevant, since they have anti-inflammatory, antioxidant, immunostimulating, as well as weak fungicidal and bacteriostatic action. Staphylea pinnata L. is an endemic plant of the Caucasus, cultivated not only in Georgia, but also in the Russian Federation in the Northern and Northwestern Caucasus. In foreign literature there are studies of antioxidant, antiproliferative and cytotoxic activity of leaf extracts of several species of S. pinnata L., as well as inhibitory activity of COX-1, COX-2 and LTB4 formation. Meanwhile, no serious Russian-language scientific studies on either the chemical composition or pharmacological action of generative organs of S. pinnata were found in the literature. This work is part of a comprehensive phytochemical study of S. pinnata. The aim of the work is to study the qualitative and quantitative composition of flavonoids in the studied object.Aim. To isolate, identify and quantify flavonoids in flowers and buds of Staphylea pinnata L.Materials and methods. Alcohol-water extracts from dried generative organs of the studied plant were used as analyzed solutions. Solutions were analyzed on a spectrophotometer SF-2000 (LLC "OKB Spectr", Russia) after sample preparation with aluminum chloride and on an HPLC Nexera-i LC-2040 (Shimadzu Corporation, Japan) equipped with a column and sample thermostat, degasser and autosampler using an individually selected elution gradient of the mobile phase (0.1 % orthophosphoric acid/acetonitrile solution). The primary data were processed using LabSolutions Single LC software (Shimadzu Corporation, Japan). Compounds from the flavonoid group were identified by retention times. Detection was carried out using a UV detector with an absorption wavelength of 365 ± 2 nm.Result and discussion. Alcohol-water extracts from flowers and buds of S. pinnata L. were obtained. Quantitative evaluation by spectrophotometry for flavonoid content was carried out. A gradient elution mode for HPLC was selected for simultaneous determination of 7 flavonoid glycosides. These chromatographic conditions allowed the identification and quantification of astragaline, cynaroside, cosmosiin, narcissin and rutin in flowers and buds of Staphylea pinnata L. Flavonoid glycosides: raponticin and kaempferol were not detected.Conclusion. Flavonoid glycosides were isolated from the generative organs of S. pinnata L., a technique for quantitative determination of flavonoid glycosides in alcohol-water extracts was developed, astragalin, cynaroside, cosmosiin, narcissin and rutin were detected and quantified.

Epistemic Class Injustice: Class Composition and Industrial Action

ABSTRACT Writings on epistemic injustice have assessed how people can be harmed in their capacity as knowers when they are a racial minority, a woman, disabled and so on. But what about when they belong to the working class? This paper is an initial attempt to understand why class has so far received limited attention within writings on epistemic injustice and to respond to these reasons. It focuses on how testimonial and hermeneutic injustices specifically harm workers in ways distinctive from the harm one might suffer due to other social identities. It does this by drawing attention to the special case of industrial strike action and the play of conceptual resources and credibility assessments that influence the action’s success. Additionally, it provides a first-time exposition for social epistemologists on what I term the ‘class compositional approach’, derived from 1960-70s Italian labour struggles. This approach, I argue, succeeds in evading the criticism of class reductionism while developing recent philosophical work on class-based injustice.